These awesome feats of human engineering are truly staggering to behold. Whether through size, complexity or beauty, it's hard to believe that these buildings, roads and more are real.

For example the Yaxi highway in China is considered one of the world's most amazing engineering marvels. Connecting Ya'an to Xichang in China's southern Sichuan province, the paved highway measures almost 150 miles, including 270 viaducts and 25 tunnels according to dangerousroads. Twisting through the clouds at times, the road is a truly staggering feat, akin to the Roman aqueducts on modern steroids. 

Other marvels include Steinway Tower, and stick-thin skyscraper that makes up part of New York City's billionaire row lining Central Park. It's hard to imagine that a building so skinny can remain stable at such heights, but Manhattan's granite bedrock certainly helps. And while the New York City skyline is certainly iconic, Shenzhen China's sprawling sea of towers is a whole different kind of profile. If you want to see stunning photos of those, along with smaller architectural spectacles - like a cool housing development in the Netherlands - check out this gallery of 20 colossal constructions and amazing architecture.