Wikimania-City/Frankfurt/Haus der Jugend
This is the exterior of the Haus der Jugend in Frankfurt, at least the main entrance and the (young) left wing of the building.
Here's one of the smaller conference rooms for more or less 15 people
This is the lunch room of the Haus der Jugend. There are two more rooms next by.
Frankfurt's skyline (I guess that this is boring for US visitors :)). The Haus der Jugend is in the very left of this picture.
Same skyline but from the position of the entrance of the Haus der Jugend. 20 meters in front of the building is the river Main.
The next pictures are taken from the largest conference room (suitable for 400 people). It is a former cinema, this might explain the tribune.