Aachen - Cathedral

The "Imperial Cathedral" was known as the "Royal Church of St. Mary at Aachen" during the Middle Ages. From 936 to 1531, the Aachen chapel was the church of coronation for 30 German kings and 12 queens.

In 792 Charlemagne ("Charles the Great", "Karl der Grosse") began the construction of a palace here and part of the whole structure was this "Palatine Chapel".
The center (and the oldest part) of the cathedral of today is this carolingian octogon, planned are realized by Odo of Metz, one of the first known architects, north of the Alps. Odo had seen obviously seen Byzantine churches. For sure he knew details of the Basilica of San Vitale of Ravenna, as San Vitale, that seems to be a model of this chapel.

Pope Leo III consecrated the chappel in 805.

The architecture of the octogon is a real hefty "power demonstration". In 805 this construction was probably near to a heavenly miracle.

Standing west facing east.

In the middle - the huge Barbarossa chandelier. Built 1165/1170 on order of Frederick I, Holy Roman Emperor, (aka "Barbarossa") and his wife Beatrix. in honor of Charlemagne and dedicated to St. Mary. The chandelier is 4,20 meters in diameters and 48 candles could be placed. It depicts the "New Jerusalem", but as it is octogonal, this Jerusalem has 16 towers nd gates instead of the more traditional 12. Even the chain, that holds it - is still the original one.

The cathedral has a very nice website - in German:
www.aachendom.de/

Wikipedia has one
in English: en.wikipedia.org/wiki/Aachen_Cathedral
and French: fr.wikipedia.org/wiki/Cath%C3%A9drale_d%27Aix-la-Chapelle