Astronomy was incredibly important to the ancient Maya. In particular, they tracked the movements of planet Venus, the sun, and the moon.

El Castillo or the Temple of Kukulcan is 98 feet tall and has 365 steps. What you can't see from the outside is the original, much smaller pyramid that acted as a foundation.

How did they get those huge blocks to the top of pyramids? There have been many speculations, but the most likely scenario involves intricate ramps.

The Great Pyramid of Giza was the tallest structure on Earth for more than 3,500 years! Workers had to cut and lay more than 200 blocks a day in order to meet their deadline.

Tourists commonly ask why the Great Wall follows a seemingly random path. The answer is intimidation and military strategy.

The first Great Wall was built from mud and reeds over 2,000 years ago. As warfare developed, the wall had to be improved and strengthened.

Restoration jobs are supposed to help fix a building, but a few hundred iron clamps did the opposite on one of the world's most well known buildings. The marble is now detaching and breaking.

A complex ramp was used to move the enormous marble blocks up to the Acropolis. Some of the largest blocks weigh over 10 tons.

Cologne Cathedral, Germany's most visited landmark, attracts an average of 20,000 people a day. Construction of the building started in 1248, but was stopped in 1473, leaving it unfinished until work restarted in the 19th century.

The Shrine of Three kings inside the church is believed to hold the remains of the Three Wise Men, whose relics were acquired during the conquest of Milan in 1164. It's only one of many stunning features within the cathedral.

Open fires were once used to heat the 1,000+ rooms in the Houses of Parliament. Engineers relied on an intense spire chimney to filter out all the smoke.

When parliament commissioned this clock in 1854, they insisted Big Ben be the biggest, most powerful clock in the world. It takes an hour and a half to wind this massive engineering marvel!

Treasures provide clues about the mysterious rulers of Teotihuacan.

See inside the secret tomb beneath the Pyramid of the Feathered Serpent.

See how the Sphinx originally appeared, and how it demonstrated the power of the pharaoh Khafre.

Clues reveal what the Sphinx Temple looked like more than 4,000 years ago, and its secret ties to the yearly equinoxes.