In reply to chris warner:
Ha ha!! I had a big drama when I arrived there, but its actually quite good...
There are two walls I know of in Hannover, one is a small thing in a gym but they did have the guidebook for the area "Klettern in Nord Deutchland," is its typically imaginative title. The routes here are quite good, but short and there is only a few of them. THe gym is good though and there is always something interesting wandering around...
The other wall is in the Campo arena
http://www.campo-arena.de/index_en.html They have all the kit you can want to hire, along with auto belays, that take a bit of getting used to. The ticket is for the whole place, so make sure you have a go on the BMX bikes, go carts and the High ropes course outside. On a climbing side the routes are really good, after five visits you will have done them all, but they also have a big overhangy roofy that is very hard and a bouldering area.
As for rock climbing, the Harz are OK, a big polished and can be crowded in summer, never tried any winter stuff there. My favourite area was called Hohenstein, its off the Osnabruck- Hannover motorway. South of the road before Hannover, there is a flattish ridge that spreads from NW to SE and there are quite a few crags along there, all in the guide book mentioned. The climbing can be a bit loose, Germans don't warn you if they knock anything off, so take a good helmet. Most routes have a smattering of bolts, but a trad rack (1 set of wires and 3 cams,) is also useful. If I could get google maps to work on this computer I could give you directions to one of the crags. I can do it on Sunday/Monday if you want. Send me an e-mail if you do and any other questions.
Jonnie
(Retired now, in Glasgow)