There has been a fortification on the castle hill since the 11th century. In 1084, Emperor Henry IV enfeoffed Wiprecht von Groitzsch, the later Margrave of Meissen and Lusatia, with the Castrum Ranis - the first documented mention. (Wikipedia)
Ranis Castle is a well-preserved fortress dating back to the 12th century and offers a wonderful view over the town of Ranis. Below it lies the Ilsen Cave, which can also be visited (regardless of the castle's opening hours).