Ostrov (Czech pronunciation: [ˈostrof] ; German: Schlackenwerth) is a town in Karlovy Vary District in the Karlovy Vary Region of the Czech Republic. It has about 16,000 inhabitants. The town proper is located on the Bystřice River in the Sokolov Basin. Ostrov was probably founded at the beginning of the 13th century. Until the second half of the 20th century, it was a small town, but then it grew significantly due to uranium mining in the region. The historic town centre is well preserved and is protected as an urban monument zone. The main historical landmark of Ostrov is the Ostrov Castle. However, the most important monument is the Red Tower of Death, which is designated a UNESCO World Heritage Site (as part of the Ore Mountain Mining Region) and a national cultural monument.