Wolfenbüttel (vôlˈfənbütˈəl) [key], city (1994 pop. 53,812), Lower Saxony, N central Germany, on the Oker River, near the former East German border. It is an agricultural market and an industrial center. Manufactures include agricultural machinery, chemicals, and musical equipment. Wolfenbüttel developed around an 11th-century castle that became (c.1280) a favorite Guelphic residence. It was the residence of the dukes of Brunswick-Wolfenbüttel (see Brunswick, state) from 1432 to 1753. The famous ducal library, founded in the 17th cent., contains about 350,000 volumes, some 3,000 incunabula, and more than 8,000 manuscripts. Its librarians included Leibniz (1690–1716) and G. E. Lessing (1770–81). Lessing's house, in which he wrote Nathan the Wise, still stands. The city's noteworthy buildings include the former ducal palace (15th–18th cent.; now a museum), a 17th-century church, and numerous 17th-century half-timber houses.