[1] The construction of Mainz Cathedral was begun about 975 under Archbishop Willigis, then regent of the Holy Roman Empire for minor King Otto III.
Its central octagon was erected from the late 8th century onwards as the chapel of the Palace of Aachen, a residence of Emperor Charlemagne.
The building, a masterpiece of the Carolingian Renaissance, has been expanded several times over the centuries; from 936 it served as the coronation church of the Kings of the Romans after their election at Frankfurt.
The present Gothic building replaced a Carolingian palatine chapel, erected at the Frankfurt royal palace (Königpfalz).
Built from 1004 onwards for the newly established Bishopric of Bamberg at the behest of the last Ottonian King Henry II and his wife Cunigunde of Luxembourg, the church is the site where the only canonized imperial couple has their grave.
The church was completed about 1170, more than 30 years after Lothair's death, by the Welf duke Henry the Lion at the time when the Imperial rule had already passed to the Swabian house of Hohenstaufen.