Altenburg (älˈtənbŏrk) [key], city (1994 pop. 46,650), Thuringia, E Germany, on the Pleisse River. Manufactures include sewing machines, apparel, and cigars. Lignite is mined nearby. "Skat," the popular German card game, originated there in the 19th cent. Built on the site of early 9th-century Slavic fortifications, Altenburg became an important trade center and was made an imperial city in the 12th cent. It formally passed in 1329 to the house of Wettin and later was (1603–72, 1826–1918) the capital of the duchy of Saxe-Altenburg. Noteworthy structures include an 11th-century church and the tower of the monastery founded (1172) by Emperor Frederick I.