A palatial sculpture park was built illegally and in secret by a self-taught artist over 36 years.

Memorial of the Salem witchcraft hysteria in the town of Danvers, where it all began.

Tiny castle in the middle of the Rhine made you pay to pass.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

Massive stele returned to Ethiopia after 70 years in Rome.

An abused and forgotten metropolis, abandoned for centuries.

The second-deepest known cave on Earth, hidden in an extremely remote mountain region.

A Turkish monastery tucked into a cliff wall.

A mailbox that saved a nature reserve.

A shrine of fire worship built on top of a natural flame.

An unoccupied lighthouse encased in layers of ice from the waters of Lake Erie.

Lebanese castle built by one man, over a lifetime.

Renaissance villa and gardens complete with a tormented colossus.

Cavernous opening completely encased in Karst limestone.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Northern Ireland's Brobdingnagian stepping stones.

The lake that fills and empties itself at random.

This stately estate house features a tower covered in a bright, modern mural.

A 30-acre garden inspired by the principles of modern physics.

Legend says this cave housed a 16th-century cannibal and his family of 48.

A snake farm famous for its venemous varieties.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.