The Great Pyramids, the Eiffel Tower, and the Great Wall of China are just a few testaments to human ingenuity throughout the ages. As building technology has advanced, so have engineers been able to create ever more impressive structures. Buildings grow taller, bridges stretch longer, and tunnels dig deeper. Indeed, some of the newest marvels seem to defy the laws of physics and nature. Learn about 20 incredible engineering feats that might merit a visit on your next vacation.

Panama Canal – Panama

At one point in history, we might have been calling this feat of engineering the Nicaragua Canal, since it was nearly built there. For centuries, traders and explorers had pondered a way to cross the Isthmus of Panama, thus saving the costly journey around South America. In the 19th century, the U.S. considered two routes — one through Nicaragua and one through Panama — before a French company began construction in the 1880s on a canal through Panama. The project failed due to poor planning and bankruptcy, but the U.S. Congress authorized the Spooner Act in 1902 to purchase the assets of the French company and continue building the canal.

Finally, the dream became reality with the opening of the Panama Canal in 1914, which swiftly revolutionized international trade. A trip through the 50-mile passage takes roughly 10 hours, cutting 8,000 nautical miles off the journey around South America’s Cape Horn. Today, around 14,000 ships travel through the Panama Canal each year.

Burj Khalifa – Dubai, United Arab Emirates

The United Arab Emirates is the site of several incredible engineering feats, and the Burj Khalifa rises above them all — literally. The tallest building in the world, it towers 2,716 feet and 162 breathtaking stories over the Dubai skyline.

Construction on the Burj Khalifa was completed in 2010 at a cost of $1.2 billion USD. Visitors can take one of the world’s longest elevator rides to the world’s highest outdoor observation deck (1,820 feet above ground) where they can enjoy spectacular views of Dubai. And on the way down, they can stop for a dip at the 39th-floor swimming pool.

Hoover Dam – Arizona and Nevada

When it was built at the height of the Great Depression, the Hoover Dam was the largest concrete structure in the world. Although it has since been surpassed by larger dams, the construction of the Hoover Dam marked the beginning of the mega-dam era. It took an army of more than 21,000 workers to complete the dam on the Arizona-Nevada border, but it was finished in 1936, two years ahead of schedule.

The project, which diverted the Colorado River through four tunnels, now produces enough hydroelectricity to power more than 1.5 million homes, and cities such as Las Vegas and Phoenix owe much of their growth to the Hoover Dam.

Three Gorges Dam – Yichang, China

Giving Hoover Dam a run for its money is the Three Gorges Dam in China’s Hubei Province. When completed in 2006, nearly a century after it was first conceived, the Three Gorges Dam was the largest dam in the world. It measures more than a mile in length and 607 feet above ground at its highest point. It also remains the world’s largest hydroelectric facility, with the capacity to generate 100 billion kilowatt-hours of electricity per year. The reservoir created by the dam is so large that ocean freighters can carry cargo inland from Shanghai.

Channel Tunnel – France and United Kingdom

With the completion of the Channel Tunnel in 1994, Britain and France were connected for the first time since the last ice age. The idea for the Chunnel, as it is affectionately known, was first proposed in the early 19th century, but it would take nearly 200 years for the dream to become reality.

‘The tunnel consists of three separate but connected tunnels which extend a total of 31 miles, including a 23-mile stretch under the English Channel. Thanks to the Channel Tunnel and a high-speed train, people can now travel between central London and Paris in a little over two hours.

Danyang-Kunshan Grand Bridge – Jiangsu, China

Danyang-Kunshan Grand Bridge runs an impressive 102.5 miles between Shanghai and Nanjing, making it the longest bridge in the world. Part of the Beijing-Shanghai high-speed railway, the bridge runs alongside the Yangtze River, crossing wetlands and rice fields. Despite having to navigate a number of challenging terrains, the bridge was completed within four years, at a cost of $8.5 billion USD. It was built to withstand earthquakes, typhoons, and even a direct hit from a 300,000-ton naval ship.

The Big Dig – Boston, Massachusetts

Traffic congestion in Boston was a huge — and worsening — problem by the late 20th century. Main arteries were congested for up to 10 hours a day, and the road accident rate was four times the national average. A project known as the Big Dig was proposed as a solution. Completed in 2007, it involved constructing a network of tunnels through much of the downtown area.

The total cost was $14.6 billion, making it the largest and most expensive highway project in U.S. history. In addition to reducing traffic congestion, the Big Dig also reduced carbon monoxide levels in central Boston and allowed for the construction of more than 45 new parks above the tunnel.

Millau Viaduct – France

Many consider the Millau Viaduct, the brainchild of English architect Norman Foster, to be a true work of art. One of the world’s tallest bridges, reaching 1,125 feet high, it is located in the Massif-Central region in southern France. The steel bridge traverses the River Tarn valley and helps to alleviate heavy tourist traffic between France and neighboring Spain. When crossing the bridge, it is not unusual to look out of one’s car window at the clouds below. The Millau Viaduct is also the world’s longest cable-stayed bridge, extending 8,071 feet.

National Stadium – Beijing, China

Beijing National Stadium, nicknamed “The Bird’s Nest,” was built to host the 2008 Summer Olympics. Designed by Swiss architects Jacques Herzog and Pierre de Meuron, the massive building has a circular shape to symbolize heaven, but many say its random geometric angles also resemble Chinese-style “crazed pottery.”

Builders used precast concrete slabs to support the seating for the stadium. In addition, the entire structure is supported by 24 columns weighing approximately 1,000 tons each. The National Stadium’s layout ensures that all 91,000 spectators can enjoy an optimal view of whatever event they are watching, from concerts to soccer championships.

Golden Gate Bridge – San Francisco, California

Surprisingly, the design of the now-beloved Golden Gate Bridge was not that popular with the public when it was first proposed. Fortunately, the plans of Joseph Strauss and Irving Morrow went ahead, and work on the bridge was completed in 1937. Now, people take more than 112,000 trips across the Golden Gate each day.

Named for the strait it crosses, the bridge is made of enough cable to circle the earth three times. Thanks to its design, which allows it to bend as needed, it can withstand earthquakes, a vital feature given its location. The striking paint job, known as “international orange,” was originally intended to be a primer, but the color proved so popular, so it remained the permanent color.

Grand Canyon Skywalk – Arizona

The Grand Canyon may be one of the world’s most recognizable natural wonders, but it is also the site of a human-made engineering feat. The Grand Canyon Skywalk is a 10-foot-wide, horseshoe-shaped walkway with a steel frame and glass floor that extends about 70 feet over the canyon’s Western Rim. It offers visitors jaw-dropping views down to the floor of the Grand Canyon, some 4,000 feet below. The Skywalk is located on the land of the Hualapai Nation and has vastly increased tourism (and income) to the Western Rim.

Akashi Kaikyo Bridge – Japan

When the Akashi Kaikyo Bridge opened in 1998, it was the world’s longest suspension bridge, though it has since lost that title to Turkey’s 1915 Çanakkale Bridge. Nevertheless, it remains an impressive structure. The bridge — which connects the Japanese city of Kobe and the island of Awaji — has a central span of 6,532 feet, and its total length measures 12,831 feet.

The bridge faced several engineering challenges: It needed to be tall enough to not block sea traffic, while also being strong enough to deal with the region’s extreme weather. Thanks to chief designer Satoshi Kashima’s ingenuity and some steel girders, an estimated 23,000 cars now cross the bridge each day.

Venice Tide Barrier – Venice, Italy

Flooding has long been a problem in the Italian city of Venice. In recent decades, the problem has worsened, and the rising waters have threatened to destroy centuries of history. Engineers hope that the solution lies in MOSE, the Italian acronym for the Venice Tide Barrier.

The concrete island (which some say resembles a James Bond villain’s lair) and huge yellow floodgates faced several decades of funding and construction issues, before finally opening in 2002. It proved its worth in 2020, when extreme high tides were held at bay. Since then, the barriers have been closed more than 30 times, helping to prevent disaster.

Bailong Elevator – Zhangjiajie, China

The Bailong Elevator makes enjoying the spectacular scenery of China’s Zhangjiajie National Forest Park much easier. What was once an arduous hike to the top of the mountains to see impressive gorges and waterfalls has been replaced by the world’s tallest outdoor elevator.

However, a ride in one of the double-story glass-and-steel cars is not for the faint-hearted, as it ascends 1,082 feet in about 90 seconds. Still, thousands of visitors each day take the Bailong Elevator (also nicknamed the Hundred Dragon Elevator) to witness the region’s natural wonders. The construction was controversial, given that the area is a UNESCO World Heritage Site, but proponents argued that it would help to prevent further erosion of delicate mountain trails.

Great Man-Made River – Libya

Several major engineering feats of the last century have involved supplying freshwater to desert regions. Funded by the Libyan government, the Great Man-Made River is one of the world’s largest irrigation projects. Work began in 1983 and is still ongoing. The project consists of a huge network of 1,752 miles of pipelines and 1,300 wells to pump water from deep beneath the Sahara Desert to cities along the coast of Libya. In addition to providing drinking water, it has made agriculture possible in vast areas of previously arid land.

Delta Works – The Netherlands

The Netherlands is one of the lowest-lying countries in the world. As such, flooding is a constant threat. The Delta Works are a system of dams and barriers built to protect much of the country from the waters of the North Sea. The Dutch Ministry of Infrastructure and Water Management began work on the project in 1954, one year after catastrophic flooding killed nearly 2,000 people.

The Delta Works were completed in 1997, although an extra storm surge barrier has since been added. As well as flood protection, the Delta Works help to improve overall water quality in the Netherlands and increase the supply of fresh water to nearby agricultural land.

Palm Islands – Dubai, United Arab Emirates

In addition to having the world’s tallest skyscraper, Dubai has made headlines with a giant human-made archipelago shaped like a palm tree. There are plans for three islands, but, as of 2025, only Palm Jumeirah is complete. The island — which took six years and $12 billion to build —  is also the only island which will be open to the public. It features apartments, hotels, and resorts, all linked to the mainland by a monorail. To create each island, more than 53 million pounds of sand have been dredged from the Persian Gulf.

Itaipu Dam – Brazil and Paraguay

Containing enough concrete to build five Hoover Dams, the Itaipu Dam stands at the border of Brazil and Paraguay. The project took a decade to complete and required moving 50 million tons of rock to shift the course of the Paraná River. One of the largest hydroelectric plants in the world, the dam contains 20 generators that can produce 14 gigawatts — enough to provide electricity to about three-quarters of all Paraguayan households, plus parts of southern and central Brazil.

Kansai Airport – Osaka, Japan

As Japan’s second-largest city grew, its previous airport could not handle the daily influx of flights and had no room to expand. The new Kansai International Airport was built in 1994 on an artificial island in Osaka Bay, connected to the mainland via a 6-mile bridge.

While the design could withstand earthquakes and tsunamis, it could not handle another unforeseen problem: The island began to sink into the muddy layer at the floor of the sea. A complex series of sensors and hydraulic jacks have resolved the issue (for now), but the solution made the project one of the most expensive airports in history, costing an estimated $14 billion USD.

New Valley Project – Egypt

The final engineering project on this list has been hailed as both a modern marvel and a mega-failure.

Egypt’s New Valley Project, also called the Toshka Project, is designed to reclaim half a million acres of desert via irrigation channels pumping water from Lake Nasser. The land will then be used for agriculture, creating millions of new jobs and allowing for the creation of new towns, a much-needed prospect for the nation’s rapidly expanding population. Construction began in 1997; however, various technical problems and skyrocketing costs mean that the project is currently only partially complete, and its future is uncertain.

It’s always interesting to see the inside of someone else’s home, but when a house is weird, wacky, or out-of-the-ordinary, a home tour becomes an adventure in and of itself. Featuring underground tunnels, secret passageways, and a dungeon or two, here are 15 of the most eccentric homes in the U.S. that are open to visitors.

Thunderbird Lodge – Lake Tahoe, California

When millionaire George Whittell Jr. bought acres of shorefront property on Lake Tahoe in the 1930s, he did so with the intention of developing a resort and casino. But after building Thunderbird Lodge, he decided he liked the privacy and kept the place to himself. 

Whittell designed the sprawling stone estate to suit his habits and needs — with a barn for his pet elephant, a card house for hosting games, and a boathouse that connected to the main house via an underground tunnel. Whittell also had the home outfitted with a dungeon, plus separate houses for the cook, butler, and caretaker. Visitors may choose to see the lodge by land or by sea — not only is the estate open for walking tours, but guests can also cruise by Thunderbird Lodge on a boat. 

Casa Neverlandia – Austin, Texas

Situated in the eclectic Bouldin Creek neighborhood of Austin, Casa Neverlandia is the life’s work of artist James Talbot. Talbot bought the single-story bungalow in 1979 for $13,000 and began pouring his creative vision into his home. Since then, Casa Neverlandia has been converted into a fanciful, three-story A-frame. To complete the transformation, Talbot incorporated physical elements from his extensive world travels, while also adding unique features, such as a truss bridge, a ship-inspired balcony, and a fire pole that leads to a bathroom. 

Keeping conservation at the forefront of his renovations, Talbot used salvaged materials, added solar panels, and installed a rainwater collection system. Both the indoor and outdoor spaces evoke a sense of whimsy, from the tropical ping-pong room to the trees covered in tile mosaics. Guided tours of the home are available for a fee; advanced reservations are necessary.

Randyland – Pittsburgh, Pennsylvania

What began as a way for a folk artist to recycle garbage turned into Randyland, a Pittsburgh landmark and the home of Randy Gilson. Decades ago, when Gilson began repurposing old items from the dump, his intention was to create homemade gifts for his family members. Over time, the project inspired him to turn his home into “Randyland,” a joyous outdoor art museum. 

By salvaging items found in the trash, he transformed his backyard into a playful space filled with colorful pop art murals, offbeat sculptures, and eccentric topiary designs. Today, the space is open to the public free of charge, offering a positive place for anyone to enjoy.

Winchester Mystery House – San Jose, California

Shrouded in strange secrets and mysterious circumstances, the Winchester Mystery House continues to confound visitors today. In 1884, the wife of firearms magnate William Winchester, Sarah Winchester, had recently inherited millions of dollars from the Winchester family fortune. After embarking on a trip around the world, the widow moved to the Bay Area and used her inheritance money to buy an eight-room farmhouse. What began as a typical family home turned into a sprawling 24,000-square-foot mansion, featuring 2,000 doors, 160 rooms, 47 stairways, 13 bathrooms, and six kitchens. 

Unfortunately, it was grief that spawned these bizarre additions — after the death of her daughter, Sarah poured herself into the home renovation for 36 years. Rumor had it that a psychic urged the matriarch to build extra rooms for all of the spirits who died as a result of the Winchester family business. Replete with staircases leading to nowhere and plenty of secret passageways, the Winchester Mystery House (which inspired the 2018 horror film Winchester) also has its share of paranormal activity, making it a popular home to tour.

Gillette Castle – East Haddam, Connecticut

If a sprawling stone castle located in the quiet countryside of Connecticut wasn’t strange enough, the interior of Gillette Castle will reveal several more eccentricities. The imposing castle is the former home of William Gillette, the stage actor who once played Sherlock Holmes. It’s also a fascinating glimpse into Gillette’s unconventional mind, with a dungeon, secret room, strategically placed mirrors, and several hidden doors. 

Built to Gillette’s exact specifications, the castle’s construction and interior features took over five years to complete, from 1914 until 1919. Since Gillette was an avid cat lover, the castle was even home to as many as 17 cats at one point, in addition to many feline-inspired toys. Now an established state park, Gillette Castle is a major draw for tourists in Connecticut, with self-guided tours available daily.

The Paper House – Rockport, Massachusetts

Aptly named the Paper House, this incredible seaside abode is made of — you guessed it — paper. Located near the Atlantic coast in Rockport, Massachusetts, the home was built by Elis F. Stenman in 1922. As a mechanical engineer who designed the machine that produced paper clips, Stenman was no stranger to paper, and he set out to build a summer cottage made of the ubiquitous material. 

Once the walls were constructed with layer upon layer of newspaper, Stenman refused to stop — he went on to paper the home’s interior, with furniture made of paper and a piano covered in paper. Although the home’s main materials are newspaper and varnish, it does contain a working fireplace made of brick and is wired with electricity. It’s also open for tours from the spring until the fall, with a small admission to guests.

Munster Mansion – Waxahachie, Texas

There was the Addams Family, and there was also the Munsters — an eccentric, Transylvanian-American family and the subject of a beloved 1960s sitcom. In fact, the Munsters were so dear to Charles and Sandra McKee that the couple built a replica of the television family’s home. Located in the small town of Waxahachie, the Munster Mansion has been recreated to mimic the fictional home occupied by the Munsters, often employing original pieces from the show’s set. 

With no blueprints to reference, the home was remodeled using footage from the television show, making it a painstakingly difficult endeavor. In addition to mansion tours of the macabre house — which features skulls, a cobwebbed piano, and a coffin-shaped phone booth — the McKees also sometimes host murder mystery parties.

Grey Towers – Milford, Pennsylvania

This formidable castle in the Poconos Mountains was the home of James W. Pinchot, the founder of the U.S. Forest Service. In 1884, the forester, politician, and businessman decided he wanted to build Grey Towers as a summer residence in his hometown of Milford, Pennsylvania. The home was built as a striking French château, complete with a pair of matching medieval towers for which the home was named. 

After the estate was passed down to Pinchot’s son, renovations continued, with the addition of a moat, fortress wall, and swimming pool. The younger Pinchot also added the home’s most famous feature, the “Finger Bowl.” The raised pool was used to accommodate dinner guests, with floating wooden bowls used as table settings. Today, self-guided tours of the National Historic Site are available year-round, seven days a week.

The Roxy Suite – New York, New York

Visiting the secret apartment in Radio City Music Hall truly feels like stepping back in time — the remarkable space has remained unchanged since 1936. The two-story apartment was fashioned for Samuel “Roxy” Rothafel, the man responsible for infusing the entertainment venue with its trademark glamour. During Rothafel’s residency, the lavish apartment was used to entertain the biggest and brightest stars in the entertainment industry, such as Alfred Hitchcock and Walt Disney. 

Featuring 20-foot-tall ceilings inlaid with gold leaf, art deco-style décor, and custom furniture, the apartment is a throwback to the glitzy days of showbusiness. After Rothafel died in 1936, the apartment was left undisturbed for decades. Since being rediscovered, the “Roxy Suite” has become a reserved VIP space for celebrities; non-A-listers can also see it by signing up for the Radio City Music Hall Stage Door Tour.

Castello di Amorosa – Calistoga, California

When you first lay eyes on Castello di Amorosa, you might feel transported to medieval Europe, instead of the rolling hills of Napa Valley, California. The 121,000-square-foot castle was built with over 1 million antique bricks imported from Europe and completed with 8,000 tons of hand-chiseled stone. The result is a stunning achievement of medieval architecture, with towers, ramparts, a moat and drawbridge, courtyards, and even a torture chamber. 

The astounding castle was the realized dream of fourth-generation winemaker Dario Sattui, who wanted to combine his love of ancient architecture with the family business. Today, the sprawling castle doubles as a world-class winery, with labyrinthine wine cellars featuring dramatic vaulted ceilings. Tours of the castle are available by reservation, complete with wine tastings of the vineyard’s finest offerings.

Alden B. Dow Home and Studio – Midland, Michigan

As an innovative architect and a student of Frank Lloyd Wright, Alden B. Dow maintained a singular motto when it came to his work: “Gardens never end and buildings never begin.” Nowhere is this credence more evident than at his personal home and studio in the small town of Midland, Michigan. When it was completed in 1941, the space became an ode to his trademark design style. 

While the mid-century home’s exterior features a sloping copper roof and contemporary geometric siding, the interior was designed to reflect the home’s natural environment. With large windows and sunroofs, vaulted ceilings, and a sunken living room at eye level with a pond, each room maintains an organic quality in tandem with the landscaping. To experience the home in person, reserving a tour 24 hours in advance is required.

Earthship Biotecture – Taos, New Mexico

The first earthship was created by Michael Reynolds, who developed the concept after moving to Taos, New Mexico, in 1969. A recent graduate of architecture school, Reynolds was frustrated by the area’s lack of affordable housing and its abundance of garbage. Killing two birds with one stone, he built his own home out of recycled tin cans. 

Today, an “earthship” is considered to be a home that is built using recycled materials, such as earth-packed tires, while also taking advantage of its natural environment. It must also use sustainable technology, such as solar and wind power, and cannot be a drain on any of the Earth’s resources. Decades after Reynolds built the first earthship, a community has been formed around this type of eco-friendly architecture. The community is open to the public, with tours of a fully functioning earthship available at the visitor center.

The Glass House – New Canaan, Connecticut

Leading 20th-century architect Philip Johnson designed the Glass House, residing in the home from 1949 until his death in 2005. Set amidst 49 acres in the Connecticut countryside, the see-through home was built to be integrated with the surrounding pastoral landscape. Despite its lack of interior walls, the Glass House is somewhat conventional, featuring a kitchen, living room, bedroom, fireplace, and bathroom. 

With its glass exterior, thoughtful interior design, and open floor plan, the glass home is also considered to be an architectural masterpiece. The architect’s property also includes the Brick House, where guests once slept, and the Studio, where Johnson worked. Built in 1980, the Studio resembles a piece of sculptural art on the grassy landscape, while the inside contains an impressive library. All three spaces are open for public tours on a weekly basis.

The House on the Rock – Spring Green, Wisconsin

The concept behind the House on the Rock began in 1945, when Alex Jordan decided to build a home atop Deer Shelter Rock in Spring Green, Wisconsin. After the home’s construction was completed, Jordan began filling the rooms with lights, mannequins, and other oddities. When word spread about the unique house, visitors started to stop by unexpectedly, and Jordan began charging for tours. 

Decades later, the House on the Rock has expanded into a huge attraction featuring multiple galleries, although the original house remains intact and open to visitors. Containing the world’s largest indoor carousel, a death-defying infinity room, and a 200-foot-long sea creature, this tourist attraction is mind-boggling in its scope and size. The Ultimate Experience Tour takes visitors through the original house and onto the Rock’s sprawling additions but requires at least three hours of continuous walking.

Glensheen Mansion – Duluth, Minnesota

On its own, Glensheen Mansion is worth a visit. The 39-room home, which stands above Lake Superior in Duluth, Minnesota, was built by Chester and Clara Congdon in the early 1900s. Since the Congdons resided in the home for 69 years, Glensheen is a time capsule of life in the 20th century, with the family’s original clothes, linens, and furnishings all on display. 

But this well-preserved historic home draws visitors for an additional reason — in 1977, it was the site of a gruesome double murder. The entire ordeal was straight out of a detective novel, including the impending trial, which put the victim’s adopted daughter (who stood to inherit the family fortune) on the defense stand. Since the home has been donated to the University of Minnesota, tours of the home and grounds remain open to visitors.