Hidden beneath the vine-covered hills of the Ahr Valley, the enormous nuclear bunker was one of West Germany's best kept secrets during the Cold War. Now, part of the bunker is open to the public.

It's a 20-minute walk from the sleepy tourist town of Ahrweiler up a serpentine path to the entrance to the new Government Bunker Documentation Center. The 9-meter (30-foot) high concrete wall marking the museum's entrance seems completely out of place among the vineyards and woods of the Ahr Valley.