degrees by Roman architecture, and in many regions, Roman and native elements are found combined in the same building. By the 1st century AD, Rome had become the biggest and most advanced city in the world. The ancient Romans came up with new technologies to improve the city's sanitation systems, roads, and buildings. They developed a system of aqueducts that piped freshwater into the city, and they built sewers that removed the city's waste. The wealthiest Romans lived in large houses with gardens. Most of the population, however, lived in apartment buildings made of stone, concrete, or limestone. The Romans developed new techniques and used materials such as volcanic soil from Pozzuoli, a village near Naples, to make their cement harder and stronger. This concrete allowed them to build large apartment buildings called insulae. Wall paintings decorated the houses of the wealthy. Paintings often showed garden landscapes, events from Greek and Roman mythology, historical scenes, or scenes of everyday life. Romans decorated floors with mosaics — pictures or designs created with small colored tiles. The richly colored paintings and mosaics helped to make rooms in Roman houses seem larger and brighter and showed off the wealth of the owner. In the Christian era of the late Empire, from 350 to 500 AD, wall painting, mosaic ceiling and floor work, and funerary sculpture thrived, while full-sized sculpture in the round and panel painting died out, most likely for religious reasons. When Constantine moved the capital of the empire to Byzantium (renamed Constantinople), Roman art incorporated Eastern influences to produce the Byzantine style of the late empire. When Rome was sacked in the 5th century, artisans moved to and found work in the Eastern capital. The Church of Hagia Sophia in Constantinople employed nearly 10,000 workmen and artisans, in a final burst of Roman art under Emperor Justinian I, who also ordered the creation of the famous mosaics of Ravenna. Medieval art Throughout the Middle Ages, Italian art consisted primarily of architectural decorations (frescoes and mosaics). Byzantine art in Italy was a highly formal and refined decoration with standardized calligraphy and admirable use of color and gold. Until the 13th century, art in Italy was almost entirely regional, affected by external European and Eastern currents. After c. 1250 the art of the various regions developed characteristics in common, so that a certain unity, as well as great originality, is observable. Byzantine art