See massive fossils that are over 200 million years old in northeastern Arizona.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

Ancient pueblos built into the base of a natural canyon wall.

The largest earthwork effigy in the world.

The largest ancient burial mound in Ohio.

The largest burial mound in the United States holds the remains of prehistoric West Virginians.

Despite its lavish ornamentation, and wholesome lifestyle of its devotees, this mountain commune has faced its share of issues.

The largest university building in the West is a gothic masterpiece containing dozens of theme rooms based on different countries.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

World's first "penitentiary," meant to be humane, drove men insane.

Copenhagen's celebrated theme park and gardens.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Famously misunderstood wonder of the ancient world

The first archaeological site discovered by aerial photography.

The largest stone circle in the world has ended up bringing up more questions than it has answered.

Europe's largest prehistoric mound – burial site of a legendary king?

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

A giant white horse drawn on an English hillside may not have been intended to be a horse at all.

A fantastic castle rumored to be the birthplace of King Arthur.