This huge pile of volcanic boulders hides a stunning network of secret grottoes.

An underwater city for the dead.

An experimental, automotive replica of Stonehenge.

At the very tippity-top of Europe is a cliff from which you can view the midnight sun.

The explorer Captain Cook may have named it White Island, but the Maori call it Te Puia o Whakaari – The Dramatic Volcano.

North Korea's massive "hotel of doom."

A precariously perched golden rock defies gravity and brings pilgrims from across Myanmar.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

One of the world's steepest streets seems to have houses sliding down it.

Remote, volcanic island that Darwin, Hooker, and the Royal Navy shaped into a thriving, artificial ecosystem.

The world's largest statue of Mao Zedong looks out over the city where he discovered Communism.

The largest cave shaft in the world is home to thousands of birds and popular with BASE jumpers.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

An alien landscape of chalk-rock in the Egyptian desert.

This tiny little island has, as the name says, just enough room for its single house.

The most alien-looking place on Earth.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

A marvel of Byzantine engineering under the streets of Istanbul.

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

This massive glowering Lenin head gazes out over eastern Siberia.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Russian Orthodox church built on an Antarctic island.

An ancient city exhumed from the depths of the ocean.

More than 200 statues filled with cryptic symbols give this park spot an aura of horror vacui fantasy.