The twinning between Ostrov and Rastatt has existed since 1991. Ostrov, a municipality of 17,000 inhabitants, formerly known as Schlackenwerth, is located at the foot of the Ore Mountains in the Karlovy Vary district. Ostrov is characterized by historic buildings such as the chateau, which is now the seat of the city administration, as well as by the historic monastery area and the early Baroque pleasure palace. The connection of the two towns goes back far into history. The Bohemian princess Franziska Sibylla Augusta, who grew up in Schlackenwerth, married Margrave Ludwig Wilhelm of Baden-Baden in 1690. Three years later, the couple moved to Rastatt.
Due to the historical relationship, the Rastatt municipal council decided in 1969 to take over a sponsorship for the former displaced inhabitants of Schlackenwerth. Close ties exist to this day. The Schlackenwerth Room in the municipal Rossi House commemorates the history of the expellees from Schlackenwerth. Their cultural heritage is also preserved here. Further information about Ostrov can be found here.