Aachen Cathedral, Germany
Emperor Charlemagne built around 800 his main residence in Aachen, the Palace and the Palace Chapel, which became the central structure of the present Cathedral and his burial place in 814.
From 936 till 1531, the Chapel was used for royal coronations and is, since 1349, an important Christian pilgrimage place every 7 years.
The Cathedral has an octagonal (8-sided) basilica and cupola surrounded by a 16-sided outer wall, and was extended in the 14th and 15th centuries with a Choir Hall and several chapels surrounding the central structure.