16. Beelitz-Heilstätten Sanatorium, Germany

Adolf Hitler was once treated for battle wounds at this hospital. Beelitz was also used as a rehabilitation center for patients with tuberculosis in the late 19th century.

17. Caddo Lake, Texas

Caddo Lake looks more like a remote swamp forest due to the old, towering cypress trees surrounding the natural lake.

18. Spreepark Abandoned Theme Park, Germany

Chilly night tours were offered for a while after Spreepark closed down in 2002. Imagine hearing weird noises from abandoned amusement park rides at wee hours. Scary.

19. Catacombs of Paris, France

An underground cemetery with overflowing century-old bones tells the history of overcrowding in cemeteries in Paris before.

20. Erta Ale, Ethiopia

Lava lakes are rare globally, but Ethiopia’s smoking mountain has two active lava lakes in Erta Ale that prove to be an extraordinary and scorching volcano.