On rare days, this abandoned castle's gatekeepers open its doors, revealing the eye-popping splendor hidden inside.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

This 16th-century monastery has been turned into a surrealist architecture compound.

The first Russian Orthodox church in the Catholic city of Rome in almost a thousand years.

The venerated body of a 12th century saint is celebrated each year with the 'Race of the Candles.'

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

A stunning hermit's shrine on a steep rocky spur in Northern Italy.

A rare example of an octagonal Catholic church.

An abandoned horror film set sits eerily along a highway through Hollywood's "door to the desert."

The largest cactus farm in Africa.

The legacy of a Moroccan Jewish community is remembered at this little mouldering cemetery.

A mud brick kasbah with a history of lavishness and traitorship.

The oldest known university in the world is in Fez, Morocco.

An eerie former warehouse turned cistern turned movie set.

An awe-inspiring mosque in Morocco with one of the tallest minarets in the world.

Traditional 11th-century outdoor tannery.

A fortified city, home to a remaining population of five families

World's largest film studio, where visitors tour the decaying sets that litter the harsh desert environment.

The remains of a magnificent medieval fortress that was the capital of a vast empire.

A Moroccan getaway in the mountain range that plays the Himalayas' stunt double.

Brightly painted boulders scattered throughout the Sinai Desert.

This ancient structure is widely thought to be the oldest intact pyramid in the world.