In the middle of a barren moorland, the remnants of a lost British Space Age stand like a 20th-century Stonehenge.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

Indents in the pavement are all that remain from a grisly death machine in Paris.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

A psychedelic labyrinth on the San Francisco bay.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

An artsy hidden staircase leads to breathtaking views of San Francisco.

Hidden beneath the streets of London is a secret subway that only carried mail.