An emerald-green grotto just a short trip from Austin.

This submersible road connecting a French island to the mainland is lined with safety towers for when the tide strands travelers.

This statue of a falling man commemorates a teenage martyr of the Hungarian Revolution.

A cabin completely covered in coffee mugs, where visitors are welcome to leave one of their own—if they can find an empty nail.

For those going through a life transition, a place to leave behind a piece of your former self.

A hand-built folk art installation covered with messages of God's love.

An old California photo stand has been turned into a shrine to the cozy art of crochet.

Derelict airplane bodies serve as both home and income for three Thai families.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Each spring, a dreamlike carpet of bluebells overtakes the forest floor.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

On the Oregon coast there is a natural hole that seems to be draining the sea.

Treehouse motel and treehouse-building school.

A whimsical village of unique treehouses resides in a Washington forest.

The remains of diamond fever taken over by the desert.

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

This ancient village and its adjoining cemetery have a beautiful history of death and remembrance.

It's hard to believe the dizzying patterns covering this abandoned mine are completely natural.

Where the White Nile River dramatically cascades between Lake Kyoga and Lake Albert in Uganda.

These medieval tunnels provided water to the city above through centuries of civil war and plague.

Why have you never heard of the second most popular tourist site in New York?

The Avenue of Mausolea is a series of grand palatial tombs.