This ancient theater was once the home of fierce gladiatorial battles.

A unique underground structure dating back to the 1st century BC.

This unusual piece of Renaissance art depicting the bodily horror of crucifixion and skin disease may have been inspired by fungus-induced hallucinations.

This small chapel built into rock is the oldest place of worship in Luxembourg.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The last bastion of Roman presence north of the Alps looms over a German town.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

An open-air sewer system that was covered piece-by-piece over 300 years.

Amsterdam's former hotspot for public executions and dissections.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

Amsterdam's Red Light District leaves little to the imagination.

Museum preserving torture methods from the past.

This spot along the 23.5 degree north parallel marks the northern boundary of the tropics.

A graceful natural rock formation stands astride the point where the Gulf of California meets the Pacific Ocean.

The lost Latin words were reconstructed using the holes from the nails that once pinned them in place.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

An ode to a soldier who came to town, fell in love, then began making his own sparkling wine.

Launched by Napoleon's soldiers more than 200 years ago, a cannonball remains embedded in the tower wall.

Often mistaken as a medieval Gothic monument, this unique cornerstone only dates back to the 1980s.

Europe's second largest ossuary wasn't discovered until 2001.

A peculiar clock commemorates a historic victory won by ringing the noonday bell an hour early.

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

Mummified monks and the accidentally interred, in a 17th-century crypt.