<P> Factors such as wealth and high population densities in cities forced the ancient Romans to discover new architectural solutions of their own . The use of vaults and arches, together with a sound knowledge of building materials, enabled them to achieve unprecedented successes in the construction of imposing infrastructure for public use . Examples include the aqueducts of Rome, the Baths of Diocletian and the Baths of Caracalla, the basilicas and Colosseum . These were reproduced at a smaller scale in most important towns and cities in the Empire . Some surviving structures are almost complete, such as the town walls of Lugo in Hispania Tarraconensis, now northern Spain . The administrative structure and wealth of the empire made possible very large projects even in locations remote from the main centres, as did the use of slave labour, both skilled and unskilled . </P> <P> Especially under the empire, architecture often served a political function, demonstrating the power of the Roman state in general, and of specific individuals responsible for building . Roman architecture perhaps reached its peak in the reign of Hadrian, whose many achievements include rebuilding the Pantheon in its current form and leaving his mark on the landscape of northern Britain with Hadrian's Wall . </P> <P> While borrowing much from the preceding Etruscan architecture, such as the use of hydraulics and the construction of arches, Roman prestige architecture remained firmly under the spell of Ancient Greek architecture and the classical orders . This came initially from Magna Graecia, the Greek colonies in southern Italy, and indirectly from Greek influence on the Etruscans, but after the Roman conquest of Greece directly from the best classical and Hellenistic examples in the Greek world . The influence is evident in many ways; for example, in the introduction and use of the Triclinium in Roman villas as a place and manner of dining . Roman builders employed Greeks in many capacities, especially in the great boom in construction in the early Empire . </P> <P> The Roman Architectural Revolution, also known as the Concrete Revolution, was the widespread use in Roman architecture of the previously little - used architectural forms of the arch, vault, and dome . For the first time in history, their potential was fully exploited in the construction of a wide range of civil engineering structures, public buildings, and military facilities . These included amphitheatres, aqueducts, baths, bridges, circuses, dams, domes, harbours, temples, and theatres . </P>

What was the central feature of a roman townhouse