The original small church was built from 1341 to 1346 to replace the old fort on the site. From 1480 to 1483 the city added a tower and from 1493 to 1504, a new nave was added.
After the Protestant Reformation in 1529, the Nydeggkirche was transformed into a warehouse for barrels, timber and grain, but in 1566 again served as worship space. Beginning in 1566 it was cleaned out and minor renovations made to the windows and walls. However, in 1568 the bell tower roof caught fire and was destroyed. The new roof was finished and the damaged clock work repaired by the end of May 1571. The large wrought iron cross which tops the main spire was built by Caspar Brükessel during the same time. The current tower's appearance mostly dates back to the 1571 reconstruction.
The later changes to the tower were fairly minor. For example, in 1625 four small embrasures or firing slits were broken out of the tower to help defend the city gate and in 1631 eight copper waterspouts were added to the roof.
Until 1721 it was a branch church of the Münster of Bern. Today's congregation forms part of the Reformed Churches of the Canton Bern-Jura-Solothurn.
In 1863, the church was extended to the west and an entrance from the Nydeggbrücke (Nydegg Bridge) was added. Then, from 1951 to 1953 a total renovation happened.
In 1956, bronze reliefs by Perincioli were inspired by medieval role models in front of San Zeno in Verona and the Cathedral of Hildesheim.References:
The Externsteine (Extern stones) is a distinctive sandstone rock formation located in the Teutoburg Forest, near the town of Horn-Bad Meinberg. The formation is a tor consisting of several tall, narrow columns of rock which rise abruptly from the surrounding wooded hills. Archaeological excavations have yielded some Upper Paleolithic stone tools dating to about 10,700 BC from 9,600 BC.
In a popular tradition going back to an idea proposed to Hermann Hamelmann in 1564, the Externsteine are identified as a sacred site of the pagan Saxons, and the location of the Irminsul (sacral pillar-like object in German paganism) idol reportedly destroyed by Charlemagne; there is however no archaeological evidence that would confirm the site's use during the relevant period.
The stones were used as the site of a hermitage in the Middle Ages, and by at least the high medieval period were the site of a Christian chapel. The Externsteine relief is a medieval depiction of the Descent from the Cross. It remains controversial whether the site was already used for Christian worship in the 8th to early 10th centuries.
The Externsteine gained prominence when Völkisch and nationalistic scholars took an interest in the late 19th and early 20th centuries. This interest peaked under the Nazi regime, when the Externsteine became a focus of nazi propaganda. Today, they remain a popular tourist destination and also continue to attract Neo-Pagans and Neo-Nazis.