Throughout the territory under the control of ancient Rome, residential architecture ranged from very modest houses to country villas. A number of Roman founded cities had monumental structures. Many contained fountains with fresh drinking-water supplied by hundreds of kilometres of aqueducts, theatres, gymnasiums, bath complexes sometime with libraries and shops, marketplaces, and occasionally functional sewers. A number of factors led to the eventual decline of the Roman Empire. The western half of the empire, including Hispania, Gaul, and Italy, eventually broke into independent kingdoms in the 5th century; the Eastern Roman Empire, governed from Constantinople, is referred to as the Byzantine Empire after AD 476, the traditional date for the "fall of Rome" and subsequent onset of the Middle Ages.