An ancient Egyptian temple in the middle of Madrid, Spain.

A neo-Gothic castle in the Argentinian countryside.

An abandoned settlement originally established by British colonialists in the Andaman archipelago.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

The largest dam in the world and the site of a potential disaster.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

The plague quarantine island home to the alleged "Vampire of Venice."

Deadly airliner crash preserved for those willing to climb and pay respects.

An enormous, 30-story-deep hole in the middle of Guatemala City.

A picture-perfect town, perfect for blowing up.

On stormy days debris from this unfinished and abandoned skyscraper rains down on the Bangkok streets.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

This abandoned Navy base was transformed into an off-grid alternative living community for thousands of people.

Nature took her revenge on the "Wickedest City in the World."

An amusement park on the grounds of an unused nuclear power plant, with a swing ride inside the cooling tower.

Site of the largest impact event to occur over land in Earth's recorded history.

This modern French ossuary contains the jumbled bones of 130,000 WWI soldiers.

Where giant ships go to die.

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

A fiery crater has been burning in the Karakum Desert since 1971.

An enormous concrete structure built over a nuclear crater.

A castle that was built stone by stone by an eccentric journalist.

Ice roads, deep holes and 3,500 pounds of diamonds.

Dr. Farid Mattar's Monument of Peace.