The Externsteine

from wikipedia:

The Externsteine are a distinctive rock formation located in the Teutoburger Wald region of northwestern Germany, not far from the city of Detmold at Horn-Bad Meinberg. The formation consists of several tall, narrow columns of rock which rise abruptly from the surrounding wooded hills. The name probably means "stones of the Egge".

It is generally assumed that Externsteine was a center of religious activity for the Teutonic peoples and their predecessors prior to the arrival of Christianity in northern Europe.

Whatever its early history, in 1093 the land surrounding the stones was supposedly bought by the Abdinghof monastery of Paderborn, as a questionable inscription inside the Stones indicate. Another dating suggests an early monastery, which might have been founded as early as 815, after the destruction of the Irminsul by Charlemagne. The findings, however, are not yet conclusive, though the dating of 1093 has been proven as false by art historians, dating the relief as early 9th century.