The writings and literature of Ancient Greece and Rome were preserved in many places throughout the Middle Ages and beyond. The Byzantine Empire is considered to be the earliest heir to the Ancient Greco-Roman intellectual legacy. This of course is not surprising considering the fact the Byzantine Empire was essentially-(at least since the early 600's AD/CE), a Greek Christian Empire. For the Greco-Byzantines, the meticulous preservation of ancient Greek writings was an important part of their cultural and ancestral heritage. (Although the Byzantines identified themselves as, "Romans" and the earliest Byzantine Emperors were primarily of ethnic Greco-Roman or Roman ethnic descent, such as Constantine and Justinian, the Byzantines, as a society, a civilization and as a people, were primarily, a Medieval Greek Eastern Christian culture).
The Arabs played a very significant role in preserving ancient Greek texts and also helped to further the intellectual legacy of the Ancient Greeks, especially in the Sciences, Mathematics and Medicine. Works by Plato, Aristotle, Hippocrates, Euclid, Archimedes and many others were translated into Arabic during the Medieval period. Averroes/Ibn-Rushd, a Muslim Philosopher from Southern Spain, was one of the earliest Aristotelian thinkers and commentators in world history.
Roman architecture was both preserved and furthered by the Byzantines, as well as by the Arabs. The Byzantine Church Dome and arches were-(and are still) directly influenced by Ancient Rome. The influence of the Roman Arch can also be found in various Islamic monuments and buildings throughout Spain and Morocco.
The Italian Renaissance-(or The Northern Italian Renaissance), is considered to have been the Epicenter of reviving the cultures of Ancient Greece and Rome, especially in its birthplace, Florence-(though it also extends elsewhere in Italy, such as Venice). During the final years of the Byzantine Empire-(around the 1400's), small, but powerful groups of political, financial and academic elites-(primarily from Constantinople/(present-day Istanbul), escaped the onslaught of Seljuk Turkish conquests from the East. This small band of Byzantine Greek elites relocated to Venice and Trieste in Northeast Italy. They brought many things, including..... several classical Greek texts that were originally preserved in the University and Monastic Libraries in and around Constantinople. These ancient Greek texts from Constantinople were subsequently translated and distributed among the growing Italian intellectual and academic classes throughout Northern Italy. In other words, Byzantine Greek elites who fled the coming Fall of Constantinople helped to pioneer and shape the Northern Italian Renaissance, as well as the early Modern West. This is rarely discussed in most mainstream Early Modern History courses, though it is historically verifiable.