The old town comprises a large number of medieval and Renaissance buildings. The "quai des Tanneurs" ("tanners' quay") is one of the most picturesque streets in Alsace. A stream used to flow in the middle of the street until the beginning of the 20th century, the relic of a former noxious-smelling trade, since tanning required large amounts of flowing water for treating and washing animal skins. Most of the old tanner houses date back to the Middle Ages and have a tall attic to provide a ventilated space for drying leather. In the neighbouring streets, "rue des Oies" ("geese street") and "rue des Veaux" ("calf street"), many houses were covered with a coat of plaster in the 19th century in order to hide the timbering, which was considered too rustic.