Folklore says this medieval fortress was plopped atop a portal to hell to trap the demons below.

A saintly relic hidden in a Prague church basement.

A spiral staircase twists to the top of this unusual Czech lookout tower.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

Thirty creepy ghosts now inhabit this decaying 14th-century church.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

Walk through Czech history in Prague's largest graveyard.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

A church of bones, decorated with 40,000 human skeletons.

Macabre astrological automaton clock dating to the late 1400s.

Two stunning 17th-century libraries and a cabinet of curiosities.

The first AIDS memorial chapel in San Francisco and one of only a few in the U.S.

Home of modern dancer famously strangled by her own scarf.

Russian history in San Francisco.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

A psychedelic labyrinth on the San Francisco bay.

Just a few miles from downtown Atlanta is a trail covered in a crazy collection of outsider art.

A wedding chapel, vintage clothing shop, and bar all under one roof.

A museum dedicated to the legacy of Bob Moog and his pioneering synthesizers.

A wonderful display of arts and crafts handmade by local artisans in the Southern Appalachians.

This holy goods emporium is where priests go for a little retail therapy to outfit their churches.

This stunning gothic ruin was a casualty of the Indiana steel industry crash.