From founding to Empire
According to a legend, Rome was founded by the twins Romulus and Remus on April 21, 753 BC. Archaeological evidence supports the view that Rome grew from pastoral settlements on the Palatine Hill built in the area of the future Roman Forum. While some archaeologists argue that Rome was indeed founded in the middle of the 8th century BC, the date is subject to controversy.The original settlement developed into the capital of the Roman Kingdom (ruled by a succession of seven kings, according to tradition), and then the Roman Republic (from 510 BC, governed by the Senate), and finally the Roman Empire (from 27 BC, ruled by an Emperor). This success depended on military conquest, commercial predominance, as well as selective assimilation of neighbouring civilizations, most notably the Etruscans and Greeks.
From the its foundation, Rome was undefeated in war, although losing occasional battles, until 386 BC when Rome was occupied by the Celts (one of the three main Gallic tribes), and then recovered by Romans in the same year. According to the history, the Gauls offered to deliver Rome back to its people for a thousand pounds of gold, but the Romans refused, preferring to take back their city by force of arms rather than ever admitting defeat.
Roman dominance expanded over most of Europe and the shores of the Mediterranean Sea, while its population surpassed one million inhabitants. For almost a thousand years, Rome was the most politically important, richest and largest city in the Western world, and remained so after the Empire started to decline and was split, even if it ultimately lost its capital status to Milan and then Ravenna, and was surpassed in prestige by the Eastern capital Constantinople.
Fall of the Empire and Middle Ages
With the reign of Constantine I, the Bishop of Rome gained political as well as religious importance, eventually becoming known as the Pope and establishing Rome as the centre of the Catholic Church. After the Sack of Rome in 410 AD by Alaric I and the fall of the Western Roman Empire in 476 AD, Rome alternated between Byzantine and plundering by Germanic barbarians. Its population declined to a mere 20,000 during the Early Middle Ages, reducing the sprawling city to groups of inhabited buildings interspersed among large areas of ruins and vegetation. Rome remained nominally part of the Byzantine Empire rule until 751 AD when the Lombards finally abolished the Exarchate of Ravenna. In 756, Pepin the Short gave the pope temporal jurisdiction over Rome and surrounding areas, thus creating the Papal States.
Rome remained the capital of the Papal States until its annexation into the Kingdom of Italy in 1870; the city became a major pilgrimage site during the Middle Ages and the focus of struggles between the Papacy and the Holy Roman Empire starting with Charlemagne, who was crowned its first emperor in Rome in 800 by Pope Leo III. Apart from brief periods as an independent city during the Middle Ages, Rome kept its status of Papal capital and "holy city" for centuries, even when the Pope briefly relocated to Avignon (1309–1337).
The latter half of the 15th century saw the seat of the Italian Renaissance move to Rome from Florence. The popes wanted to equal and surpass the grandeur of other Italian cities and to this end created ever more extravagant churches, bridges and public spaces, including a new Saint Peter's Basilica, the Sistine Chapel, Ponte Sisto (the first bridge to be built across the Tiber since antiquity), and Piazza Navona. The Popes were also patrians of the arts engaging such artists as Michelangelo, Perugino, Raphael, Ghirlandaio, Luca Signorelli, Botticelli and Cosimo Rosselli.
The period was also infamous for papal corruption with many popes fathering children, and engaging in nepotism and simony. The corruption of the Popes and the extravagance of their building projects led, in part, to the Reformation and, in turn, the Counter-reformation.
Towards the reunification of Italy
Italy became caught up in the nationalistic turmoils of the 19th century and twice gained and lost a short-lived independence. Rome became the focus of hopes of Italian reunification when the rest of Italy was reunited under the Kingdom of Italy with a temporary capital at Florence. In 1861 Rome was declared the capital of Italy even though it was still under the control of the Pope. During the 1860s the last vestiges of the Papal states were under French protection. And it was only when this was lifted in 1870, owing to the outbreak of the Franco-Prussian War, that Italian troops were able to capture Rome.
After a victorious World War I, Rome witnessed the rise to power of Italian fascism guided by Benito Mussolini, who marched on the city in 1922, eventually declared a new Empire and allied Italy with Nazi Germany. This was a period of rapid growth in population, from the 212,000 people at the time of unification to more than 1,000,000, but this trend was halted by World War II, during which Rome was damaged by both Allied forces bombing and Nazi occupation; after the execution of Mussolini and the end of the war, a 1946 referendum abolished the monarchy in favour of the Italian Republic.
Rome grew momentously after the war, as one of the driving forces behind the "Italian economic miracle" of post-war reconstruction and modernisation. It became a fashionable city in the 1950s and early 1960s, the years of la dolce vita ("the sweet life"), and a new rising trend in population continued till the mid-1980s, when the comune had more than 2,800,000 residents; after that, population started to slowly decline as more residents moved to nearby surburbs.