Aalen, city, Baden-Württemberg Land (state), southern Germany, on the Kocher River, at the northern foot of the Schwäbische Alb (Swabian Alps), 30 miles (48 km) north of Ulm. It originated around a large Roman fort, much of which remains; nearby are the remains of the Roman limes (frontier wall). It became a free imperial city in 1360 and was severely damaged by fire in 1634. It passed to Württemberg in 1802. The old city hall dates from 1636 and the church of Sankt Nikolaus from 1765. The Limesmuseum of Roman relics was opened in 1964. In 1975 the adjoining city of Wasseralfingen was annexed to Aalen, enlarging it by nearly a third. A communications centre, Aalen also has machinery, optics, textile, and paper industries. Pop. (2005) 67,066.