To anyone that may be interested...
last week I was at the Stuttgart (the german one :) airport waiting for the plane and I found that they have a nice small "museum" with some engines (piston and jets, even a Tornado RB-199 engine) and other plane items and on the roof there are some interesting planes: an An-2, a Me-108 Taifun, an AT-6, a PZL built Mil Mi-2 and a couple of others. To go to the roof and see the planes you have to pay a small fee (2 Euro if I'm not wrong), but it was too snowy and cold to go there and they can be seen even from the windows. I wouldn't go to Stuttgart just to see the exhibit, but in case you are there and have some time to spend while waiting for your plane, it's more interesting than duty free shops.
Btw, while we were there we sighted a plane on the other side of the runway that looked like a 707 but was too dark to be a civil plane... then we saw it taking off and realised it was a KC-135: wow! Nice add-on to all those boring civil planes :)