An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

The spectacular subterranean collection includes dazzling minerals, including a piece of "kryptonite."

This "cursed house" features secret rooms, hidden vaults, and dark escape tunnels.

A subterranean world of tunnels links several buildings of this rare 19th-century asylum.

The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Railways may have forged this quintet of lovely tunnels, but now they are open to hikers.

The largest geyser field in the southern hemisphere is a spectacular sight.

This enchanting rainforest hotel looks as though it grew from the forest itself.

A beautiful deserted greenhouse in the middle of a park.

One of Chile's most active volcanoes is riddled with beautiful caves.

The “City of Stairs” sits high in the Andes, above the world’s largest underground copper mine.

A record-breaking pool that uses computers to turn ocean water into cleaner, private swimming water.

A fantastical group of cliffside stairways, bridges, and twisting paths carved out of stone provide a surreal coastal hike.

A sculpture of a giant hand reaches for the stars in the middle of the Atacama desert.

This Japanese-inspired labyrinth of hot springs is hidden in a Chilean forest.

The largest stone moai on Rapa Nui.

This odd Chilean waterfall-cano hotel must be entered via a rope bridge.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

Massive rock sculptures formed during the time of the dinosaurs still stand undisturbed.

A toxic lake near a volcanic caldera that is home to flamingos and other life.

105-foot wide giant metallic flower blooms anew every day in the heart of Buenos Aires.

A gateway to a mysterious network of underground tunnels.

A bright little alley in La Boca is a part of tango history.