The Middle Ages is broadly defined as the period between the fall of Rome, with its centralized imperial rule, and the revival of classicism in the Renaissance. Thus medieval architecture is often assumed, however wrongly, to turn away from classical influences and classical aesthetics. The Medieval period encompasses about 1,000 years of European history from the 5th to the 15th centuries and is traditionally broken down into the Early Middle Ages (400s-900s), which includes the Carolingian Empire (700s-800s) and the Ottonian Empire (800s-900s), and the Later Middle Ages, which includes the Romanesque (1000s-1100s) and the Gothic (1200s-1400s). The expression "middle ages," or "medieval," refers to an early historical prejudice against this extensive historical time frame when the classical world was initially replaced by such regional groups as the Visigoths, the Ostrogoths, the Franks, the Saxons, and the Celts, who carved out local power and asserted their own beliefs, customs, and architectural practices. Since these cultures were ultimately unified under Christian authority in Rome, it was the Christian church that emerged during the Middle Ages as the most important patron of architecture. Medieval architecture consists of churches, monasteries, palace complexes, castles, and government buildings. Some of the earliest medieval churches built outside of Rome are found in Spain and were constructed by Visigoths who had converted to Arian Christianity in the fifth century, settled in Spain, and by the sixth century had established themselves as the elite class, ruling over the native peoples of the Iberian Peninsula.
The small Church of Santa Maria de Quintanilla de las Viñas located outside Burgos is one of the few surviving regional churches from the seventh century. It was originally a basilica-plan church with a nave and flanking side aisles that opened into the choir through two doorways.The choir was the same width as the church, and therefore gave the impression of either a transept or two flanking sacristies. Classical Roman architectural features blend here with regional pagan imagery, while Visigothic elements such as the notable horseshoe arch over the entrance to the apse attest to the rich confluence of cultures that typifies this period. Finally, the Islamic conquest of the Iberian Peninsula in 711 added another element to the rich cultural mix that informed both architectural style and sculptural decoration at this time.
The Carolingian Dynasty (768-877) is largely defined today by the rule of Charlemagne, or "Charles the Great," who was crowned Holy Roman Emperor in 800 by Pope Leo III in recognition of his work in establishing Christianity in the territories he conquered across modern-day France, western Germany, northern Italy, Belgium, and Holland. This alliance between secular and sacred Europe took place in a lavish ceremony held at Old Saint Peter's Church in Rome, where Charlemagne was compared to Constantine and urged to continue his expansion of Christian territories across Europe. Charlemagne began his career as a strong military leader among his native Frankish peoples, who had settled in an area around the Rhine River some three centuries earlier. He then rose in stature to become the leading secular authority in Europe. During his reign, he purposefully cultivated the use of Imperial symbols in his court in Aachen, Germany, to reinforce this alliance with Rome. Through his study of the Latin language and patronage of classically inspired art and architecture, Charlemagne revived the culture of classical Rome.
Charlemagne's palace complex in Aachen is largely destroyed today, but documents detail a lavish compound of houses, administrative buildings, and shops set near the hot springs outside central Aachen. Begun in 794, a partially surviving audience hall and his palace chapel are all that remain today. The chapel, constructed like an imperial mausoleum, recalls San Vitale (c. 520) in Ravenna, Italy, in its octagonal ground-plan, dome, and ambulatory, yet its original source is the Roman tholos, or round domed funerary building that was later adapted by Early Christian builders for use as a Christian martyrium or baptistery. The earliest example of this type of martyrium is Santa Costanza in Rome, the mausoleum built for Constantine's daughter around AD 340 and later modified for use as a church in the mid-13th century. Charlemagne would certainly have seen this and many other buildings during his visit to Rome, and these buildings would have helped him transfer this Imperial Roman style to northern Europe. Charlemagne's chapel is shaped into an octagon with a gallery topped by clerestory windows. Eight compound pilasters rise to a round arch above the clerestory level, and pairs of Corinthian columns repeat at both levels between the pilasters. These are the elements that make the most direct visual link to classical architecture. An ambulatory surrounds the central core at the ground level, while the eight corners follow through up into an eight-ribbed dome. The chapel also has a western façade with towers on either side that house spiral stairs leading to a second-story throne room and a third-story room that held the chapel relics.
Many other seminomadic peoples lived across Europe during this time, but what makes the Christian rulers important to the discussion of architecture is that they used permanent buildings as a potent symbol of unified authority. The Carolingian Empire was continued by the grandsons of Charlemagne but ended in the 9th century with almost no new architectural development. However, it was replaced in the 10th century by a powerful Saxon court from modern-day Germany and Austria, in what had been an eastern region of the Carolingian Empire. This new European power was called the Ottonian Empire, named after its three major rulers, Otto I (called "the Great"), Otto II, and Otto III, and it was this empire, due to its connections to the papacy and marriages in the Italic Peninsula, that led to the formal establishment of the Holy Roman Empire, which continued in some form down into the 20th century.
The Ottonians also sought to use architecture similar to the grand constructions in Rome as a means of defining their authority across various regions. Thus, their church of Saint Cyriakus, in Gernrode, Germany, begun in 961, reflects both Ancient Roman influences and local aspects of construction by German stonemasons. Its original façade was covered several centuries later with a protruding apse, but beneath the apse, one can still detect a tripartite division of the façade with three round-arched, bifurcated windows in the upper register of the central façade, which is flanked by round towers. The upper portions of the towers reveal a row of flat pilasters, carved in low relief to suggest the type of tower arcade that might have been found on an early Christian church in Rome. Aside from this fictive arcade and the window articulation, the exterior of Saint Cyriakus is very severe. Inside the church, the nave has three registers, while the nave arcade alternates round columns with square piers to create an A-B-A-B rhythm. Above the round arches of the arcade, a triforium gallery is formed with a different rhythm, in which six columns alternate with thick square piers down the arcade. The uppermost register features small arched clerestory windows. Transept chapels flank the choir at the east end of the basilica-plan church, while a side door allowed the nuns of the convent to enter the church through a separate portal.
Archbishop Gero of Cologne and Bishop Bernward of Hildesheim were important patrons of architecture during the Ottonian era, and the Benedictine Abbey Church of Saint Michael's, built in Hildesheim from 1001 to 1032, is one of the finer examples of Ottonian architecture. Destroyed in World War II, the church was re-built in the 1950s and is now considered a UNESCO World Heritage Site. The church features a choir at either end, in keeping with the layout of the Ancient Roman basilica, which lacks the strongly axial direction of most subsequent churches. Towers are located at each crossing, which provides a more complex exterior plan as well. On the interior, the nave arcade is articulated with alternating columns and piers in an A-A-B-A-A-B-A-A rhythm, while the walls rise up without a triforium into small clerestory windows located beneath the flat timber roof. This ceiling recalls Ancient Roman coffering more directly than at Saint Cyriakus, as here the ceiling is divided into more obviously square panels. The most famous feature of the Church of Saint Michael, however, is its set of bronze doors that rise up three times taller than human scale and are modeled with Biblical scenes in a narrative format that anticipates the intricate portal sculpture of the later Romanesque and Gothic eras. Both the Carolingian and Ottonian Empires were important in the formation of an architectural language that brought together the Ancient Roman world, early Christian symbolism, and important regional influences to accommodate the dramatic growth of the Church through the Middle Ages, a growth that continued through the next several centuries.