For many centuries, Mainz has been surrounded by a city wall. Along the wall are several guard towers, some with foundations dating from Roman times. The Eisenturn is one of these guard towers along the city wall, however, it is a little more modern... it was constructed in the Middle Ages, during the 13th Century.
The tower was badly damaged during WWII, but was repaired and restored in the 1970s. During this time, the city wall on either side of the tower was removed.
This tower was built in 1240 as a watch tower. It was one of 34 towers of the old citywall. Its name derives from the iron market that was held in front of the tower. Today it is used as an art gallery.