TROPPAU (Polish, Oppava; Czech, Opava), the capital of the Austrian duchy and crown land of Silesia, 180 m. N.E. of Vienna by rail. Pop. (1900), 26,725. It is situated on the Oppa river, close to the Prussian frontier, and is a well-built town with extensive suburbs. The industries comprise the manufacture of cloth, industrial machines, sugar-refining, jute fabrics and brewing. Troppau was founded in the 13th century; but almost its only claim to historical mention is the fact that in 1820 the monarchs of Austria, Russia and Prussia met here to deliberate on the tendencies of the Neapolitan revolution. This congress of Troppau, however, left nearly the whole matter to be considered and decided at Laibach. The former principality of Troppau is now divided between Austria and Prussia, the latter holding the lion's share.