The Ortenburg sits at the highest point of the old town, a low stone fortress with origins in the 10th century and a long history as the seat of regional governors under successive rulers — Bohemian, Hungarian, Saxon. The complex now houses several institutions including the Sorbian Museum and the Saxon Higher Regional Court.
The castle's most striking feature is the Matthias Tower with its late-Gothic relief of Matthias Corvinus on horseback above the gate. The courtyards and ramparts can be walked at any time without a ticket, and the view from the western terrace down to the Spree and the Alte Wasserkunst is one of the best in town.