Aachen Cathedral, a Roman Catholic Church in the city of Aachen in Germany, is considered as one of the oldest cathedrals in Europe. Frequently referred to as the Imperial Cathedral, it was known as the Royal Church of St Mary in Aachen during the Middle Ages. The cathedral is immensely significant in terms of architecture and is one of the best preserved architectural monuments of the Carolingian period. Built on the line of the churches of the Eastern part of the Holy Roman Empire, it was splendidly enlarged in the Middle Ages.

Originally, Aachen was a Roman spa called Aquisgranum and it rose to prominence in the late 8th century during the rule of Charlemagne, when he made it his favourite residence and gradually it became a centre of Western culture and learning. For 600 years, from the coronation of Otto in 936 until 1531, the Aachen chapel was the church of coronation for 30 German kings and 12 queens. The city was fortified in the late 12th century and became a free imperial city in about 1250.

The foundation stone of the Aachen Cathedral was laid sometime around 790 AD by Charlemagne, along with the towers of his Palatine Chapel. After his death, Charlemagne was buried in the chapel in 814 and after he was canonized in 1165, the chapel became a draw for pilgrims.

However, his remains were later transferred to the Shrine of Charlemagne in the Cathedral altar, adorned with engravings of the King and Pope Leo III, who crowned Charlemagne as the Imperator Romanorum, Emperor of the Romans, in the year 800.

The great dome of Aachen Cathedral above its altar is octagonal, as Charlemagne placed special significance on that particular number, which appears frequently in the Holy Bible. In fact, it was charged with symbolism in the Christian world during medieval times. It is interesting to note that an octagon can be made by drawing two intersecting squares within a circle. While the circle represents the eternity of God, the square represents the secular world. The four corners represent the four directions to heaven, as well as the four characteristics of man. Charlemagne saw the number eight as symbolizing the power of the Franks and the Roman Empire, the ruler of both the secular and religious worlds.

The Cathedral was built in the form of an octagon with the choir and chapels and the octagon takes the core position of the cathedral. It is decorated with golden mosaic pictures with the God and twenty four Ancients around Him. Apart from that the interior is also decorated with fascinating statues and the grave of Charlemagne, marked by a stone slab over which hangs a huge bronze chandelier presented by Frederick I Barbarossa in 1168. The chandelier is inscribed with a dedication to Mary from Barbarossa and his wife Beatrix. The high altar and the Imperial throne are located on the upper circuit of the Palatine Chapel in an octagonal side room. An octagonal drum, with window openings rises, is located above the arches of the gallery and is crowned with a cupola. Much later, a Gothic Coir was built to the east of the octagon between 1355 and 1414.

There are two golden shrines elevated inside glass boxes in the Gothic choir. The one closest to the Octagon is the Shrine of the Virgin Mary or Marian Shrine (1238) and the one in the back is the Shrine of Charlemagne (1215). The Shrine of the Virgin Mary contains the Four Great Relics of Aachen, which include the shroud of the Blessed Virgin, the God’s loincloth, the Jesus’ swaddling band and the cloth on which the head of St John was placed after his beheading.

The city of Aachen, including its famed cathedral, was heavily damaged during World War II, when the choir hall, the Neo-Gothic altar, a large part of the cloister and the Holiness Chapel were completely destroyed. Reconstruction and restoration process continued intermittently for a prolonged period, which finally took more than 30 years to complete.

Aachen Cathedral became the first ever German cultural monument to be added to the UNESCO World Heritage List in 1978.