In Central Germany's Alma valley, a striking 17th-century castle overlooks the picture-postcard scenery that stretches in every direction; jutting majestically above green trees and bathed in sunshine, it looks more like something out of Cinderella than a former Nazi headquarters. And yet the story of Wewelsburg Castle is irretrievably intertwined with the insanity and cruelty at the very heart of the Third Reich.

In 1933, SS-Reichsführer Heinrich Himmler, the second most powerful man in Germany, chose the stronghold as the site of a new Nazi Mecca, a place he planned to transform into the very "centre of the world". His efforts to turn this vision into reality would claim the lives of over 1,200 people.

Over the years, Wewelsburg has become a symbol of the alleged Nazi obsession with the occult.