This North African stone complex is considered to be the oldest astronomical observatory on Earth.

A registered historic landmark shrouded in unsettling local legends.

An abandoned Gold Coast-era mansion once intended for the exiled ruler of Albania, who never arrived.

An unexpected sinkhole in a desert flat within Gold Butte National Monument.

Deep vertical fissures like miniature slot canyons cut across the cemented volcanic rock of Black Point above Mono Lake.

Abandoned bridge hidden deep in the San Gabriel Mountains.

At high tide this strange footbridge appears to have no purpose whatsoever.

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

A museum befitting the city responsible for supplying the majority of the world's LSD.

A surviving concrete arrow from a 1920s navigational network is preserved right off a modern freeway.

This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

Sacred waters rescued from the wrath of a volcano.

Established over a thousand years ago, this family-run teahouse continues to serve skewers of sweet rice cake to this day.

This lower Manhattan bar is set up in an old bank vault that rests beneath a skyscraper that hides even more historic splendor.

Nikola Tesla's former home contains an homage hidden from plain sight.

There's an exclusive Beefeaters pub hidden in the Tower of London.

A secret door leads to this cozy dive that sells only “milk.”

Cool down and fill up after visiting Teotihuacán at this bar and restaurant in a deep, underground cave.

Lions carved into the rockface adorn these two tombs built into the mountains of Dadan.

This is one really big nut.

An abandoned marine theme park has created a difficult experiment in dolphin rewilding.

Ruined pieces of stone and a swimming pool are all that remain of an amusement park swept away by a flood.

This abandoned amusement park was built on a site with a dark history.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.