Centuries-old bridges grown from tangled roots.

This lovely little bridge hidden in a Switzerland gorge is essentially a fairytale.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

Once the longest bridge in Ireland, this rusting span sits abandoned and overrun by nature.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

They call this long foot bridge a swinging bridge, but really it's the bouncing you have to watch out for.

This Maine bridge may be the last wire-supported bridge of its type in the world.

One of the windiest peaks in Crimea is home to an incredible set of cable bridges.

Despite being pillaged and destroyed a number over times down the centuries, this historic church still sort of stands.

One man single-handedly dug a road right through a mountain after his wife died due to its interference.

Stunning examples of Russia's 18th-century wooden architecture.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

The youngest volcano in Central America.

These broken shards of ancient ruin may hide an ancient pyramid.

What is it about mushrooms that makes people wish they lived inside of them?

Keshwa chaca, among the last handwoven Incan bridges, crosses Apurimac Canyon in Peru.

The only road through the heart of Glacier National Park.

An abandoned stretch of elevated road in the middle of the Brazilian jungle.

These Stalin-era industrial 'death traps' hang lifeless above the city

The underground sanctuary of a mysterious ancient cult.

Naturally formed rock city in Poland.

This series of Scottish caves has no clear purpose other than baffling historians.

This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.