Altenberg Abbey, Odenthal, Medieval Cistercian monastery in Odenthal, Germany

Altenberg Abbey is a former Cistercian monastery whose church, the Altenberger Dom, was begun in 1259 and consecrated in 1379. Built of grey stone, it has a tall nave with a steep dark roof, a row of tall pointed windows, a tower with a pointed spire near the right end, and a chevet of tall windows with flying buttresses. In front and to the left, lower flat-roofed buildings with dark roofs and a small red-roofed section enclose paved courtyards.

Founded on 25 August 1133 as a daughter house of Morimond, the abbey was first installed in Burg Berge, the castle of the Counts of Berg, who had moved to Schloss Burg. The monks soon relocated to the Dhünn valley, where a Romanesque basilica was consecrated in 1145 and 1160. In 1259 the foundation stone of the present Gothic church was laid; its choir was consecrated in 1276 and the whole building on 3 July 1379. The abbey was dissolved in 1803 and restored from 1847 under King Frederick William IV of Prussia.

The name Altenberg first appears in 1195, distinguishing it from Neuenberg, the castle at Burg an der Wupper. Since the church's restoration from 1847 under King Frederick William IV of Prussia, it has been used simultaneously by Protestant and Catholic parishes. The Gothic church, dedicated to the Assumption of Mary, has no towers, only a roof turret, in keeping with Cistercian building rules.

The site is open daily for visitors to explore the grounds and buildings at their own pace. Guided tours focusing on the architecture and monastic history are available through the information center, with weekend options for more specialized exploration.

The Markuskapelle by the Dhünn, built around 1225, is the oldest surviving chapel on the abbey grounds and shows the Rhineland transitional style between Romanesque and Gothic. The abbey's first church, a three-aisled Romanesque basilica, had been consecrated in 1145 (choir) and 1160 (nave) before the Gothic Dom replaced it.