The imposing castle dominates the image of Blankenheim. Finds indicate that a Roman fort previously stood here. Gerhard I built the castle in 1115 above the source of the Ahr. Today the castle complex serves as a youth hostel and can be visited on request. Blankenheim Castle is located directly on the hiking trails Burgen-Route and Eifelsteig stage 6.
The magnesium-calcium mineralisation here comes from sandstone and claystone as well as overlying volcanic rock. The high content of carbonic acid originates from the Eifel volcanism and gives the water the name ‘Säuerling’ (acidulous). A total of five springs are known in Birresborn, several of which were of great economic importance. Today, drinking water can be taken from the Lindenquelle and the Fischbach-Drees.
Holzstraße is home to several heritage-protected buildings. Although the air raid on 16 November 1944 destroyed huge areas of the town centre, some houses on Holzstraße managed to survive this attack virtually unscathed.
The Afelskreuz (Ablasskreuz) stands on an old Roman military road. For centuries pilgrims have been pilgrimage from Bonn-Cologne to the grave of the Apostle Matthias in Trier.