Material Drachenfels trachyte, was part of the in 1133 founded Cistercian Abbey Altenberg. Untill 1511the Church also served as a grave to counts and Dukes von Berg and the Dukes of Jülich-Berg. From 1255 built on site of Romanesque building. Count Adolf IV had laid the cornerstone of the Cathedral on 3 March 1259 in the presence of Archbishop Konrad von Hochstaden and is thus as old as the Cologne Cathedral, its choir was consecrated 1287, 1379 the Archbishop Cologne ordered the consecration of the total church and done so by Bishop Wikbold Dobilstein (buried in the choir). The large West window was 1400 built in. 3-Beech Basilica with ambulatory and seven choir chapels, and seven choir, here is Cistercian barrenness mixed with North French shapes. According the building code of a Cistercian order it only has one Flèche and no towers. Coloured glazing and figurative representations were missing in the early years. Its Interior has a strict form of Gothic, the same strict linear structure is also applied in the deviding of the main nave, the oldest of Windows are located in the ambulatory. After secularisation in 1803 its inventory was auctioned off in 1804, in 1806 the temporary owner (Bavarian King Maximilian Joseph) sold Church and Abbey to wine merchant Johann Heinrich Pleunissen from Cologne for 26.415 Reichsthaler, the buildings were leased toa chemistry factory which produced Prussian blue. An explosion and subsequent fire in the night of 6 to 7 November 1815 destroyed buildings and church roof. In 1830 collapse of important parts of southern transept, adjacent choir d and crossing (junction of the four arms of a cruciform), from then on it fell rapid in decay. Multiple owners switched off and on, eventually its debris was partially used as stone quarry. In 1834 Franz Egon von Fürstenberg-Stammheim acquired the Abbey Church and took the first (inadequate) measures. After a donation from the church ruins to the Prussian State the restoration of the Abbey Church was significantly supported by Friedrich Wilhelm III (more than 70% of construction costs, about 100,000 crowns) with the proviso that in the future it would serve as a simultaneum. A physical separation in a Catholic and an evangelical part was originally planned but was rejected by King Friedrich Wilhelm IV. The first Protestant prayer service took place 13 August 1857. Further restoration phases were carried out 1894-1912, as well as in ' 60, floor heating was built in but was out of working order quickly.