One man's extraordinary topiary garden in a small South Carolina town.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

This park contains one of the largest concentrations of cedar glades, a unique and rare ecosystem.

Known for the tunnel that leads visitors to the water.

Longest canal tunnel in the world, abandoned in the 1960s.

Shakespeare, David Bowie, Dr. Who, the Saxons, Druids and Romans are all claimed to have all made their mark on these massive man made tunnels.

The atmospheric road was never meant to be so creepy.

An exquisite tunnel of cascading flowers.

This Costa Rican topiary park is a surreal garden of unearthly delights.

The entrance to this sinisterly named tunnel hides behind a Tim Hortons.

An abandoned railroad tunnel forgotten by time awaits inquisitive hikers.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

Every winter, the wind carves blocks of frozen water into beautiful abstract shapes inside this unusually curved tunnel.

The romantic botanic tunnel feels like a well-kept secret.

These abandoned grain silos and tunnels are an urban exploration dream.

A centuries-old forgotten underworld lies beneath Malta.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.

This ancient tunnel is one of the most important examples of Roman hydraulic engineering in Spain.

A spooky defunct railroad tunnel now part of a sprawling trail.

Away from the crowds of fishing enthusiasts, take a hike deep into the woods and journey into an eerie darkness.

Located more than 600 feet beneath the North Atlantic seabed, this tunnel boasts the world's first undersea roundabout.

A crack flared at the base provides a pathway completely through a sandstone ridge near Moab.

The longest enclosed pedestrian bridge in the world spans 14 lanes of traffic and six rail tracks, all while lighting up the night sky.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.