The ruins of Frýdštejn Castle (German: Burg Friedstein) can be found in the Liberec Region, Czech Republic, near the town Turnov. It is one of three castles in Jablonec nad Nisou District. A typical rock castle, it lies on the upper end of a long sandstone rock ridge, next to the village of Frýdštejn (former Zásada). The castle dominates the nearby Jizera river valley and the old trade route from Turnov to the north.