May 2018 Print

The Domed Basilica of Charles the Great

by Dr. Gerald L. Browning

The warm, bubbling waters that dotted the countryside of an area known today as Aachen in Western Germany were there well before men came to build their castles and churches. These thermal springs which originated deep below the marshy wetlands were a favorite place for Neolithic hunter-gatherers who had discovered their wonderful healing qualities for their battle wounds and for the rigors of early farming. The baths or the thermos gallo as the Romans would later call them, were quite simple in construction, probably small stone buildings with arched entrances leading into ceramic, water-filled enclosures with plumbing systems that allowed the water to run through them. Here, men could bathe and clean themselves in pure, mineral comfort.

The springs were important enough for the Romans to establish early cities there. Julius Caesar, in his famous letters concerning the Gallic campaign (58-51 B.C.), remarked how the spas were important reasons for claiming Gaul. “The Gauls had many things tending to luxury as well as civilization.” He also described in vivid detail the attitude of the Gauls toward the spas. “…they bathe promiscuously…a large portion of the body being in consequence, naked.” The springs were so desirable that beginning in the first century A.D., the lands around Aachen were fought over by succeeding waves of invaders, first the Celts from Brittany, then followed by Romans, Muslims, and Goths. Later, Carolingian kings were said to have loved luxuriating in the aquae spadenae or the warm fountains that the Romans had built and enjoyed using with family and friends.

The Spread of Christendom

By the sixth century A.D., the areas around Aachen had become thoroughly Christianized by monks such as St. Benedict and St. Gregory. Here, the great Carolingian kings who had conquered and inhabited the area began to build stone fortresses to protect their western borders from the ravaging invaders who were pushing inexorably toward them. By the eighth century, the region had been consolidated under the Carolingians—a Frankish tribe and their king Charles (The Hammer) Martel.

In the year 732 A.D., the Empire was beset by the Moorish invasions from Northern Spain. Engaged in a momentous battle in the city of Tours, the Carolingians achieved a remarkable victory. For many centuries to come, Muslim armies would be denied any military entry into Carolingian territory. Martel would later comment that he saw his armies as the protectors of Christendom. As the Carolingian Empire grew in territory, eventually encompassing lands stretching from Europe to Asia Minor, its Christian monastic structure spread exponentially. By the time Charles the Great (the grandson of Martel) came to the throne in 768 A.D., Europe was dotted with monasteries reflecting the theology of some of its greatest men, including Benedictines, Gregorians, and Northumbrians. Christian scholars such as Einhard and Alcuin were yielding great influence on the king. Alcuin would become responsible for organizing the “Emperor’s program to revive knowledge in the Empire.” Churches were being built in the villages and likewise cathedrals in the cities. Missi dominici or the royal messengers of Charles were sent throughout the countryside to instruct the populace in matters of theology and religious practice. The arms of Christ were being spread by the king. Charles was reputed to have learned to read and write by using an early Christian Bible and it was believed throughout the kingdom that he retired to bed each evening with both sword and Bible next to him. He encouraged the construction of monastic schools as well as the copying of sacred works of art and literature. Models of Christian morals and conduct (exempla) were explained to his people in the form of “ admonition generalis” or orders of the king. Einhard, the legendary biographer of Charles, describes vividly how the stadium discendi (the zeal of learning) was raging through the kingdom.

Determining a Fitting Site

So it was determined, perhaps in the year 766 A.D. when Charles’s father Pepin was still king, that Aachen would be the site of both the palatium (palace) and the domed basilica. For the next thirty-six years, according to the available modern archeological records, palace and church were completed. Charles dedicated his church to the Virgin Mary. A small, gold-adorned ceramic figure of her still greets the visitor as he approaches the alter of the modern basilica. The basilica was the seat of Carolingian Christian rule throughout the eighth and ninth centuries. It legitimized the Carolingians not only as kings, but as the secular leaders and protectors of the faith-second only to the pope whose spiritual ascendancy in Peter’s church was without question. So it became a symbiotic relationship between the regency in Aachen and the papacy in Rome. Mutual interests between the king and pope were maintained and new ones propagated. This became strikingly apparent in the later years of Charles’s rule (800 A.D.) when he was confronted with the dilemma of a weakened papacy under Leo III. Historians are divided as to who initiated the historic meeting between Charles and Leo on Christmas day of that year. We know that Leo was under great political pressure, owing to rumors of personal and financial problems associated with his office. There existed powerful Roman families allied against him, to the point where his personal safety was an issue. Issuing an invitation to the king whose rule was unquestioned, could help his overall position in Rome.

Charles, on the other hand, could benefit greatly from the visit. It would solidify his position as the unrivaled leader of a disparate and diverse empire if he came to the aid of the beleaguered pope. Above all, it would ensure his fealty to the pope since he was coming to Leo. This is significant; the Christian king making a pilgrimage to Rome. But it also reaffirmed the love and respect the king had for God and Rome. This fact cannot be overestimated. Charles was first a Christian and then a king. The history of his family was as the protector of the Faith. The blood of his people had been spilled on the Christian battlefield over the last two hundred years. Moors from Spain; Vandals from Africa, Vikings from Scandia; all had sought to rape, burn and pilfer what men such as Augustine, Jerome, and Benedict had built.

The meeting was greatly advantageous to Leo because his ulterior motive was to elevate his position as pope in the face of a mighty king. On that fateful day, the day of Jesus’s birth, the pope placed the crown of Holy Roman Emperor on the head of Charles. The king kneeling at the foot of the pope was startling for both its political and religious significance. The pope was now establishing the papacy as the overseer of the Empire. All succeeding kings would supplicate themselves in homage to the pope. The papacy would now enter a new era in which its religious authority over the king was without question. This would be the case for the next one thousand years as kings from the newly emerging nations of Europe would all reign in the name of the cross. We don’t know if Charles really cared about this. He was busy ruling from his castle and his dome. But we do know that he cared about the stability of the papacy. He ran down the enemies of Leo, established control of Rome and returned to Aachen satisfied in his efforts. The years 800 A.D. to 814 A.D. are the height of his rule as both king and follower of Christ. And it was during this time that the fruits of his labor to build his church were realized. His vision is the stunning cathedral that occupies the center of Aachen today.

The following descriptions are the result of Charles’s vision.

The Dome and the Basilica

The early basilica was based on the Eastern Byzantine design method, principally the use of the octagonal concept of church design. This included the use of domes, arches, and columns which would characterize later Roman design (400-600 A.D.). Scholars believe that much of the architecture of Aachen’s basilica was based on that of San Vitale the stunning northern Italian basilica built by the Emperor Justinian in the mid-fifth century A.D. As with other castles in Germany, the basilica formed one of the cornerstones of its defense. Circular in nature so that it was difficult to ascend, and with carved beveled slits, it formed a protective stone bulwark against attack. It was essentially an eight-sided box of stone with each side supported by a columned arch. A squinch or a stone octagon allowed the box to assume eight sides with eight columns. The columns were equal in size-kept together by “traveling arches” that led into one another and finally formed a perfect circle. Some theologians have suggested that the octagonal design of the dome represented the “eighth day of the creation as the new redeemed creation of God. The walls of the castle merged with it to form an outpost for observation into the surrounding countryside, announcing its presence to friend and foe, a pillar of God standing in the way of the brutal men who attempted to destroy it. Although the basilica today is made of grey granite and slate, originally it was covered in red brick with a wooden superstructure and a flat roof as opposed to the merging semi-globes of the roof today. One might say that the dome encompassed the Christian world as Charles saw it; a world of no boundaries, encircled by the Christian God, universal in scope, eternal in vision, and united against all enemies in the life of Christ. To Charles, it was perhaps the embodiment of St. Peter’s but set into the wilderness of central Europe. He may have even seen it as the “new Jerusalem.” Such was the love of the Carolingians for their church.

The Interior of the Basilica

The interior of the Aachen basilica is wondrously embellished compared to the somewhat nondescript, plain exterior. William Fleming, in his panoramic work Arts and Ideas describes how the “Christian basilica turned the Greek temple outside in.” We do not know what it looked like in 800 A.D. but today, it is beautifully adorned. When one enters the narthex or main entrance of the church he looks in a somewhat north-south direction since the nave is elongated with a semi-circular apse surrounding the altar. Seats for the clergy were placed along the walls on either side of the nave’s ambulatory with a matroneum for women forming a vaulted gallery around the interior of the nave. On the second of three stories, high above the altar, the throne of the king was placed, apparently so that he could peer down on his congregation as they prayed. There is, throughout the basilica, a distinct sense of looking vertically. Fleming suggests that the eye “is led from the central floor space to the dome.”

Surrounded by the figures of his adoring disciples and Charles, Christ looms lovingly from above as the Messiah or the “Lord or protector of the universe.” His life is depicted through the medium of mosaic art in which thousands of tiny glittering pieces of glass or ceramic (tesserae) were fused together to form a picture. They were delicately placed on a bed of wet mortar with the “cartoon” of the figure already drawn. The process might be seen as a medieval style of paint by numbers. When the tiles were in place, tiny reflectors of silver and gold were sprinkled on them to make them shimmer like a thousand stars. When the light entered through the glass windows of the apse, the effect was stunningly beautiful as if the interior space was illuminated with colored streams of gleaming light. One scholar described the light emanating as the “inner radiance of the spirit” of God. Today the mosaics are beautifully preserved on all three floors of the basilica, perhaps 1,200 years after their initial installation.

The Windows

Although the windows were first built in 1355 A.D. and replaced many times over, the present ones were installed after World War II. They form the East wall of the choir section directly behind the altar and the golden coffin-shrine of Charles. That they point eastward may be in recognition of the high recognition that Charles held for Constantinople. They are supported by eight limestone archways made of limestone and measuring over 25 meters in height. Today, the glass is a marvelous mixture of blue, purple, and red glass that rises up within the inner curves of the dome. Its leaded panels tell a story both of the great king who inspired it, and of the history of the Christian church. When the sun shines, the light streams through the glass in colored rays. Unlike its later cousins—the cathedrals—where the dark, thin shadows of light conceal much of the glass’s beauty, the dome allows for the light to spill onto the altar. It is as if God had stood above His church and ministered His heavenly light upon His flock. It is only fitting that today the cathedral is called the “glass house of Aachen.”


The Basilica of Aachen has stood for twelve hundred years. Parts of it have weathered with age, or suffered destruction in war, or simply been modernized. But its majestic windows, mosaics, and columns have continued to sparkle. Its dome, together with its attached medieval spires, continues to dominate the skyline of Aachen, Germany. Today, it is the seat of the Holy See and remains a working episcopal Catholic church with German priests and nuns, a lovely choir, and a vibrant community of adherents. Hence, it is appropriate that at 10:00 a.m. on a warm, sunny morning, the author was in attendance as Mass was said. The Gospel delivered that day was of Mt. 16:13-19. The words were a fitting tribute to Peter who had just been given the keys to heaven. The priest spoke in German. “You are Peter, I will give you the keys to heaven.”

One can just see the great King Charles with the keys to the grand bronze doors of his cathedral—his heaven on earth. Einhard best describes the scene. “He cherished with the greatest fervor and devotion the principles of the Christian religion, the basilica he adorned with gold and silver…and was a constant worshipper at this church—going morning and night.”