According to one tradition, Rome was founded by Romulus in 753 b c e . Archaeological evidence indicates that the city resulted from the federation of a group of villages (the process known as synoecism), located on four hills (the Capitoline, Palatine, Esquiline and Quirinal) overlooking the Tiber floodplain, with the Forum (once a cemetery) as communal ground. It probably reached an urban size and degree of complexity by the early sixth century, when it was ruled by kings. In 510 b c e , the Romans rejected kingship and, for the next 400 years and more of the Roman Republic, the city was governed by elected magistrates and popular assembly. Monarchy returned in 27 b c e in the form of the principate (from princeps, first citizen - a republican term) of Augustus, who would assume the title imperator(whence ‘emperor’, though in its original meaning, a military general); his successors continued to rule Rome until the collapse of its empire in the West, in the fifth century c e . Roman cities were evidently built within a shifting ideological context; the sequence of tyrannical, republican and imperial forms of government and administration is broadly comparable to developments in ancient Greece (see Table 3-1, on p.83, for a framework of ancient Roman history).