This historical swimming pool near Miami is emptied and refilled each day with naturally filtered water.

This attraction was abandoned after the Chornobyl disaster.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

Mysterious craters may have been home to an ancient cult.

A cathedral resurrected from the ashes of one of Europe's greatest urban fires.

Man-made mineral caves house massive bat colony.

Historic slum of Tartu.

This medieval Estonian tower provides access to a series of tunnels that have been home to soldiers, punks, and fine art.

The Guardian of Tallinn.

An empty relic of the Moscow Olympics crumbles away in Estonia's capital.

A former imperial sea-fortress and Soviet prison.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

A 125-meter long "tribute to the Brazilian people."

This massive Brazilian church is built like an angular, technicolor pyramid left by Mayans from the future.

This insurance company building reminds customers that witches, bears, and gnomes are out there, best be insured.

An alien church provides much needed silence in the midst of a Finland shopping center.

Super-heavy Nazi architectural experiment.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

Berlin's old airport.

The oldest teak bridge in the world is made from the remains of a royal palace.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.

A wooden replica of France's famous tower.

This small Estonian hill is covered in hand-made twig crosses that are said to bring good luck.