An existential riddle in the world's largest ancient castle.

The ruins of an ancient stadium that hosted gripping chariot and horse races.

The largest brick bridge in the world.

A symbol for the opposition to nuclear power around the world.

A tiny chapel clings to a precipice above Germany’s gemstone capital.

A statue of the second-tallest Dutchman in history.

All that remains of the fishing-vessel-turned-warship is its weathered hull.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

The control tower at the historic weapons range is now available as a highly unusual vacation rental.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

A line of abandoned, alien-like fortresses dot the mountains of North Italy.

This small window display is dedicated to the noble carrot.

A cross marks the spot in a small Scottish village that claims to be the exact center of the country.

The storied English village that pretended to be insane inspired NYC's nickname and the fictional namesake in the DC Comics universe.

This fountain of a little boy that spits on passersby at erratic intervals is a town icon.

Every half hour the eye-rolling clock face sticks out its tongue to mock the good citizens of Koblenz.

The geoglyph once sported a glass bottle eye.

The 14th-century ruins are said to contain healing powers.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

A former Nazi lookout tower with a magnificent view of the Rhineland.

Ralph Waldo Emerson spent two years living here decades before it became a Frederick Law Olmsted-designed park.

Real bones which are said to have belonged to a Polish dragon.

This hanging crocodile is thought to be the "dragon" that once plagued a Czech city.