Hello All,
I am currently living in Bielefeld, (a Brit, non military, but with several connections - my Uncle started off flying a Sunderland in the war and stayed on to do some interesting things later in his career).
This is the location - as Heathrow Harry says:
https://goo.gl/maps/8QNSXMNsZPv
Some good pictures there but I am happy to go up to the viaduct to take some more if you like, I do have a couple I took in April to send to a friend who is ex RAF, but I'm afraid I am unable to upload the best one for some unknown reason, the one attachment to the message will give you an idea of the old and "new" parts of the viaduct.
This site provides a bit more information:
Bielefeld Various
My German wife, who grew up here, says the area was flooded after the war because of unexploded ordinance (as ShyTorque mentions), thus creating a nice walking and wildlife area.
As for the Bielefeld conspiracy, I deny it all....but then I suppose I would!