Just watched a bit about a secret Nazi bunker where 'the bell' was held, were anti gravity testing was apparently undertaken and where 'Foo-fighters' were sighted frequently, (no not Dave Grohl and the band but the WWII call sign for UFO's).

(Repeated at 00:50 and More 4 + 1 starts at 11pm)
Website here:
http://www.channel4.com/culture/microsites/W/weirdworlds/alien_history/Cheers
The Commander