In the course of time it was bell tower, dungeon, treasure chamber for the county's archive and today as little museum which houses exhibitions from time to time. During the bombing night of September 11, 1944 in WWII , it was heavily bombed, but reconstructed in the 50-ies.
Today, it's also one of Darmstadt's main meeting points :-)
Guided tours are available; the tower is open Wednesday 15:00-19:00 and Saturday 13:00-17:00.
Update January 2008:
new weblink below (still German only) and revised opening hours.

