The town's perimeter wall (Stadtbefestigung) is 2 300m long and has four gates. Until the 19C they remained the only way into the town. Every 30m bastions called Wiekhäuser were built. Of the 56 constructed, 26 have been rebuilt. Town citizens of military age were recruited to man these battle stations. Defence of the gates themselves was the responsibility of the town's principal guilds: the Bakers, Wool Weavers, Shoemakers and Smiths.