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

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

Hundreds of thousands of concrete bunkers crowd Albania long after the fall of Communism.

Macabre astrological automaton clock dating to the late 1400s.

This ancient cave temple complex is the largest and best-preserved temple complex in Sri Lanka.

A pocket of jungle amidst urban expansion in Panama.

Central America's deepest lake is actually a volcanic caldera, surrounded by three volcanoes.

Monkeys inhabit the lush forest surrounding ancient Mayan ruins once considered sacred.

These roaring primates were considered a divine creature in the cosmology of the Maya.

Deep in the Guatemalan jungle stands an ancient pyramid that once marked the reign of a king.

At least seven hues of blue and turquoise make this freshwater lagoon unique.

A hidden treasure of an abandoned city lies deep in the jungles of Campeche, Mexico.

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

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

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

Found down a long dirt road, a sacred Mexican cenote and 18th-century hacienda remain hidden.

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

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Traditional 11th-century outdoor tannery.

Thousands of narrow alleyways in an ancient medieval city make up what's believed to be the world's largest car-free urban zone.

Vast stretch of tide-pools with a unique Moroccan charm.

Fortune tellers, snake charmers, poets, and storytellers all gather on this historic square in Morocco.

A black cat protests the City Guild in Riga's Old Town.

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