Monument to a brutal, ineffectual US bombing campaign and a sobering reminder of the human cost of the Vietnam War.

A Surreal flight of architectural fancy in Vietnam's Central Highlands.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

The oldest working mechanical clock in the world.

A unique hotel for the artistic soul.

This Slovak bridge is known both for its connection to a national uprising and its UFO-shaped eatery.

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

An ancient knight and a symbol of the city's freedom.

Gargoyle head that brings good luck.

A wunderkammer of gold and silver reliquaries and ancient saintly bones.

A tiny church on a man-made island in the Adriatic.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Every equinox this Maya pyramid puts on a spooky ancient light show.

A treasure trove of astronomical, mathematical, and scientific instruments at Cambridge University.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

An ornate plague column – built to celebrate life – claimed the lives of numerous artisans during its construction.

Man-made cave with enigmatic carvings, some say made by the Knights Templar themselves.

Vast fan-shaped British cemetery honouring American servicemen lost in World War II.

Venice's island of the dead.

100 year tradition of fist fights, marked by marble footsteps.

This massive subterranean fissure is known as the "underground Grand Canyon."

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A whimsical bridge adorned with decorative dragons.