Mathematikum is 0.5 mi (0.9 km) from central Giessen, why not stop by during your stay. If you want to experience more of the culture Giessen has to offer, head to Gleiberg Castle, Liebig Museum, and Hessenhallen.
You can spend an afternoon browsing the exhibits at Liebig Museum during your trip to Giessen. Wander the forest or discover the area's hot springs.