Ostrov and Rastatt have been twinned since 1991. The 17,000-inhabitant municipality of Ostrov, formerly Schlackenwerth, is located at the foot of the Ore Mountains in the district of Karlovy Vary. Ostrov is characterized by historic buildings such as the castle, which is now the seat of the town administration, as well as the historic monastery area and the early baroque pleasure palace. The connection between the two towns goes back a long way in history. The Bohemian Princess Franziska Sibylla Augusta, who grew up in Schlackenwerth, married Margrave Ludwig Wilhelm von 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 on a sponsorship for the home association of the former displaced inhabitants of Schlackenwerth. Close ties still exist today. The Schlackenwerth Room in the town's 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.