A psychedelic labyrinth on the San Francisco bay.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Museum dedicated to the terror regimes of Hungary.

Once the home of a hermetic monk, this cave now houses a small church.

At more than 5,000 years old, these structures are among the oldest free-standing stone buildings in the world.

These temples are among the oldest free-standing stone buildings in the world.

The ruins of a megalithic monument sit right in the garden of a luxurious Maltese resort.

Overshadowed by other, more famous Maltese catacombs, this ancient burial chamber has one of the best examples of a ritual agape table.

This subterranean necropolis holds three floors of antler-dug grave caves.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

This Stone Age solar temple aligns with the sun on each equinox and solstice.

A secluded oasis of contemporary art and natural beauty.

An ancient necropolis of magnificent tombs.

Once part of an ancient international harbor, it's now an all-you-can-eat shrimp buffet for flamingos and other water birds.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

A collection of objects supposedly singed by the hands of souls in purgatory.

Jesus' footprints and the first catacombs in the world.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

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

A Victorian natural history and ethnographic museum with wonderful turn-of-the-century, science-book-esque evolution displays.

A hands-off space for graffiti artists to hone and display their skills.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.