The palatine chapel of Aachen was built by order of Emperor Charlemagne and designed by Odo of Metz. Construction began in 792 and it was always categorized as a cathedral. Later, it was consecrated to the Virgin by Pope Leo III in the year 805. It also underwent restorations in 983 and 1881, so it has Gothic and Renaissance additions.
The palace courtyard area has been preserved, surrounded by later buildings in which remains of the old factory were used. Furthermore, it is easy to guess the general plan of the complex as it was in the time of Charlemagne. The palace has preserved its layout around a rectangular patio.
On the opposite side of the Aula Regia was the Palatine Chapel, which is the only vestige preserved in the entire complex, despite some transformations and two important restorations in 983 and 1881.
It follows an architectural scheme already used in the past, taking as a reference the configuration of churches such as San Vitale in Ravenna from the time of Justinian, being, in turn, a model for later constructions. A large atrium with exedras, reminiscent in plan of one of the imperial porticos of Rome, preceded the chapel. It is a centralized double-body building, with an octagonal central core covered with a dome. This body is surrounded by a hexadecagonal ambulatory two levels high, with its sections covered by groin vaults. The ambulatory is interrupted in the eastern area by a rectangular head, although it is not preserved.
The dome was probably based on the Dome of the Rock of the legendary Temple of Solomon, common in medieval imagination. The entrance body defines a Westwerk structure, with a balcony for the appearance of the monarch. This communicates with the royal tribune, inside, on the ambulatory, where Charlemagne's throne is located. The proportions of the building are much slimmer than those of San Vital, especially in the upper area of the central body where, in each of the eight sections, there are two superimposed levels of pairs of banked arches. On the other hand, in the palatine chapel the horizontal lines are accentuated "by the very shapes of the structure and even by adding notable imposts throughout the entire central area." Charlemagne was buried in the chapel, in a Roman sarcophagus replaced at the beginning of the century by the current urn-reliquary of gold and precious stones. It should be noted that there is a notable contrast between the richness of the building and Charlemagne's throne, the latter being very simple.
The interior is decorated with polychrome marble brought from Ravenna and Rome, highlighting the chromatic alternation of the voussoirs of the arches in white and dark green. The roofs, including the dome, were decorated with mosaics that are not preserved today, the current ones being the work of the centuries and .
Eginardo points out in his Life of Charlemagne that the emperor ordered ancient columns to be brought from Rome and Ravenna to create this space, although the most valuable ones were looted in the century by the Napoleonic armies and taken to Paris, and not all of them could be recovered. Charlemagne required several elements and materials from the Byzantine city of Ravenna. The interior sumptuousness of its buildings fascinated Charlemagne and he sought to link his power with that of the great emperors Constantine and Justinian using art as legitimizer. These materials added to the strategy of assimilation of Aachen as a new center of power in Europe that had already been sought on the building's floor plan. Eginardo's chronicles say that the materials came from Rome and Ravenna, so it follows that this work made the construction of the Palatine Chapel extremely expensive and difficult. In this way, the reuse of these elements does not address issues of cheapening, but rather its objective was to endorse Carolingian power through art.
In short, in this imperial complex, of which only the chapel remains, a great Roman imperial influence is reflected. This is due to Emperor Charlemagne's desire to turn Aachen into the power center of his empire. Assimilating this work with that carried out by Justinian in Constantinople, turning it into the new Rome in the century. For this reason, its construction is inspired by great architectures such as the church of San Vital in Ravenna. Materials for the decoration of the chapel were also collected from this city, which was the capital of the Western Roman Empire after the division by Theodosius in the 19th century. With these plunder Charlemagne tried to legitimize his power through art. Despite not knowing with certainty the subsequent influence that the Palace had, due to the destruction that the buildings have suffered throughout history, we see some affiliations such as the octagonal oratory of Germingy-des-Prés or the church of Ottmarsheim in Alsace.
The construction, which includes barrel vaults, groin vaults, and an octagonal cloister vault in the dome, reflects late Roman or pre-Roman practices rather than the Byzantine techniques used in the church of San Vitale, and its plan simplifies the complex geometry of the Ravenna building. Multicolored marble slabs are used to create a sumptuous interior. The chapel makes use of ancient spolia, possibly from Ravenna—Eginardo claimed they were from Rome and Ravenna—as well as carved materials. The bronze decoration is of great quality, especially the doors with lion heads and the interior railings, with their Corinthian columns and acanthus leaves.
The dome was originally decorated with a fresco, and later with a mosaic. In the Baroque period it was replaced by stucco. The original mosaic was reproduced in the century with the same iconography as the original. It depicts the twenty-four elders of the Apocalypse wearing crowns and standing around the base of the dome. Above the main altar and facing the royal throne, there is an image of Christ in Majesty.
[7] The upper gallery of the chapel was the royal space with a special throne area for the king, and then the emperor, which allowed entry into the liturgical space of the church and also into the outer atrium.
The main entrance is dominated by a monumental entrance facing west and comprising the western façade. It includes the entrance hall, rooms on one or more upper levels, and one or more towers. These face the church atrium. The addition of the west doorway to churches is one of the Carolingian contributions to Western architectural traditions.