If you've visited the Leaning Tower of Pisa or the Taj Mahal, you know that they are spectacular testaments to human ingenuity. And, modern technological advances have allowed us to create even more amazing structures over the last century. In fact, buildings keep getting taller and more gravity-defying as time passes.

As you plan your next trip to some exciting locations, don't forget to put these four engineering feats on your list of must-see destinations.

National Stadium, Beijing, China

Path leading up to Beijing National Stadium
Credit: CEphoto, Uwe Aranas

The brainchild of Swiss architects Jacques Herzog and Pierre de Meuron, Beijing's National Stadium (nicknamed "The Bird's Nest") was built to host the 2008 Summer Olympics. The massive building gets its nickname from the twisted, lattice-like steel struts encircling its exterior.

That said, the National Stadium's circular shape (symbolizing heaven) also attests to its extraordinary character. The inside of the stadium seats 91,000 spectators, with room for an extra 11,000 temporary seats.

It took an astronomical 14,700 precast concrete slabs to hold the seating for the entire stadium. And, that's not all: the entire structure is supported by 24 columns weighing 1,000 tons each. In all, the stadium measures 333 meters (about 1,092 feet) long, 294 meters (about 964 feet) wide, with its highest point reaching 68.5 meters (about 225 feet).

Although the size and design of The Bird's Nest is amazing, the stadium also focuses on the spectator experience, making it a truly incredible engineering feat. Visitors always have an optimal view of sporting events, no matter where they sit.

Burj Khalifa, Dubai, United Arab Emirates

Burj Khalifa and Dubai skyline
Credit: shutterlk/ Shutterstock 

Modern Dubai has defined its relevance on the world stage through its reality-defying skyscrapers and stunning man-made islands. As a testament to its profound resilience, the city boasts structures that continually test the boundaries of conventional engineering.

The Burj Khalifa, modeled after the Empire State Building, is one of the most recent of Dubai's incredible engineering feats. It's the tallest building in the world and rises more than 2,700 feet into the air. The building also boasts an astounding 162 stories. For the sake of comparison, the Burj Khalifa is two times as tall as the Empire State Building and three times as tall as the Eiffel Tower.

The Burj Khalifa also holds many other world records, such as the most number of stories, the tallest free-standing structure, the highest occupied floor, the highest outdoor observation deck (at about 1,820 feet), and the tallest service elevator.

After a design competition brought the world's most innovative building designers to Dubai, the Burj Khalifa was born. Its structure is basically an abstract manifestation of a Hymenocallis flower, more commonly called a spider lily. This was the design that beat out the other competing designs. Thereafter, construction began in January 2004 and took 1,325 days to complete. The $1.2 billion dollar project had 12,000 international workers hustling to get the job done at the height of the building process.

If you've seen Mission Impossible: Ghost Protocol, you may have noticed the Burj Khalifa in it. During an especially tense scene, Tom Cruise leaps out of a window and then runs down the building supported by just a cable. Although most of the tower has private residences, visitors may choose to stay at Armani Hotel, the world's first hotel designed by famous fashion guru Giorgio Armani. And yes, the Armani Hotel is located in the Burj Khalifa itself.

Grand Canyon Skywalk, Arizona, USA

Grand Canyon Skywalk  on canyon edge
Credit: StanislavBeloglazov/ Shutterstock 

The Grand Canyon is one of the greatest natural wonders of the world. And, it's the incredible Grand Canyon Skywalk that makes it possible for visitors to experience its majestic beauty in an entirely new way. Located near Eagle Point at Grand Canyon West, the Skywalk is a 10-foot wide, horseshoe-shaped walkway with a steel frame and glass floor. The vertigo-inducing structure juts out onto the canyon about 70 feet from the Western Rim. It's supported by box beams built from two-inch-thick plates, containing hollow spaces that are each 32 inches wide and 72 inches deep. The beams are designed to resist wind-induced structural vibrations.

The structure is essentially a U-shaped cantilevered bridge. Meanwhile, the Skywalk itself sits 4,000 feet above the floor of the Grand Canyon. What most visitors may not realize is that the Skywalk belongs to the Hualapai Tribe.

The genesis of the Skywalk project centered around delivering long-term financial support for the Hualapai Nation, who owns the land, as well as giving visitors a stunning and unmatched vantage point.

After careful testing and construction, the Skywalk opened to visitors in 2008. Prior to its construction, the Western Rim of the Grand Canyon only saw about 75,000 visitors per year. Today, the panoramic view offered by the Skywalk has converted the Western Rim into a must-see spot for Grand Canyon visitors; the Hualapai Tribe now welcomes more than 1,000,000 visitors per year.

Three Gorges Dam, Yichang, China

Three Gorges Dam in China
Credit: gyn9037/ Shutterstock

For decades, Nevada's Hoover Dam was the structure held up as a major engineering feat. Although it still stands as a modern structural miracle, China's Three Gorges Dam gives it a run for its money. Located on the Yangtze River slightly west of Yichang in China's Hubei Province, Three Gorges Dam was the largest dam structure in the world when construction ended in 2006.

The dam is more than a mile long and rises 607 feet above the ground at its highest point. Three Gorges Dam is also the largest hydroelectric project in history; in fact, it remains the world's most productive hydroelectric dam, producing 22,500 megawatts of electricity at a time. It has the capacity to generate 100 billion kilowatt-hours of electricity a year. Incredibly, the entire dam is supported by 28 million cubic meters (37 million cubic yards) of concrete and 463,000 metric tons of steel.

The dam also has a reservoir that allows large ocean freight-liners to carry cargo from Shanghai to inland China. Despite its benefits, the dam almost didn't get built. Concerned stakeholders debated its construction and potential drawbacks for decades. After concerns over its inevitable displacement of villagers, the project sat on the back burner for more than 40 years. The dam was finally completed in 2015, almost 100 years after the project was first envisioned. Today, it stands as one of the greatest engineering marvels of the modern world.