AKA Royal Church of St. Mary at Aachen and the Imperial Cathedral, or in German, Kaiserdom
Aachen Cathedral is a Roman Catholic cathedral found in Aachen, Germany. It is the oldest cathedral in northern Europe and is a UNESCO World Heritage Site.
When Charlemagne conquered Europe and was 'unexpectedly' named Holy Roman Emperor by a zealous pope, he took it to heart. In 786 AD he started a project to create a 'Second Rome'. The centerpiece of this project was the Palace of Aachen, which included a number of impressive buildings; one of the most impressive of these was the Palatine Chapel, which would in turn become the centerpiece of the Aachen Cathedral.
The chapel itself was the most impressive single area of the finished cathedral. It was capped with the largest dome north of the Alps, 16,54 meters wide and 31 meters high, designed with an impressive merger of Byzantine and Germanic-Franconian elements. The copula is octagonal, supported by eight massive pillars. The effect is both massively solid and soaring. It became a model of other cathedrals built in the following centuries, starting some of the architectural trends that became part of the Carolingian Renaissance.
Various buildings used by the priests and clerics of the chapel were built to make the overall structure form the shape of a latin cross; this initial floorplan included a curia to the East, clerical offices to the North and South, and an ornate atrium with exedrae to the West. Later on many other additions were made, including a choir hall, a steeple, and several additional chapels, including an impressive glass chapel on the 600th anniversary of Charlemagne's death.
The original chapel was consecrated in 805 by Pope Leo III, the same pope who crowned Charlemagne as the Imperator Augustus five years earlier. In the following 730 yeas Aachen Cathedral was the coronation church for thirty German kings, cementing it as an important cultural landmark for the Germans, in addition to its central role for believers and religious pilgrims.
Aachen Cathedral is also the burial place of Charlemagne. He died in 814, and was 'buried' the same day in an ornate crypt. A later ruler, Otto III, claimed to have opened the tomb and found that Charlemagne had been laid to rest seated upon a throne in full regalia. His remains have been moved twice to newer caskets, but he still rests in Aachen Cathedral to this day. Charlemagne was canonized in 1166 by Antipope Paschal III, making the cathedral an important site for pilgrims who come to visit his tomb and assorted relics.
Aachen Cathedral is also the home of the Cross of Lothair, a thousand-year-old and heavily jewel-encrusted cross of some artistic merit and impressive value. This is of interest to pilgrims and art historians alike.
Sources:
UNESCO Site
Wiki: Aachen Cathedral
Wiki: Palatine Chapel