During the Renaissance, the Strozzi family ruled over Siena while waring with the Infamous Medici's of past time Florentine.

The Roman origin accounts for the town's emblem: a she-wolf suckling infants Romulus and Remus. According to legend, Siena was founded by Senius, son of Remus, who was in turn the brother of Romulus, after whom Rome was named. Statues and other artwork depicting a she-wolf suckling the young twins Romulus and Remus can be seen all over the city of Siena. Other etymologies derive the name from the Etruscan family name "Saina," the Roman family name of the "Saenii," or the Latin word "senex" ("old") or the derived form "seneo", "to be old".

Siena did not prosper under Roman rule. It was not sited near any major roads and lacked opportunities for trade. Its insular status meant that Christianity did not penetrate until the 4th century AD, and it was not until the Lombards invaded Siena and the surrounding territory that it knew prosperity. After the Lombard occupation, the old Roman roads of Via Aurelia and the Via Cassia passed through areas exposed to Byzantine raids, so the Lombards rerouted much of their trade between the Lombards' northern possessions and Rome along a more secure road through Siena. Siena prospered as a trading post, and the constant streams of pilgrims passing to and from Rome provided a valuable source of income in the centuries to come.

The oldest aristocratic families in Siena date their line to the Lombards' surrender in 774 to Charlemagne. At this point, the city was inundated with a swarm of Frankish overseers who married into the existing Sienese nobility and left a legacy that can be seen in the abbeys they founded throughout Sienese territory. Feudal power waned however, and by the death of Countess Matilda in 1115 the border territory of the Mark of Tuscia which had been under the control of her family, the Canossa, broke up into several autonomous regions.

Siena prospered as a city-state, becoming a major centre of money lending and an important player in the wool trade. It was governed at first directly by its bishop, but episcopal power declined during the 12th century. The bishop was forced to concede a greater say in the running of the city to the nobility in exchange for their help during a territorial dispute with Arezzo, and this started a process which culminated in 1167 when the commune of Siena declared its independence from episcopal control. By 1179, it had a written constitution.

This period was also crucial in shaping the Siena we know today. It was during the early 13th century that the majority of the construction of the Siena Cathedral (Duomo) was completed. It was also during this period that the Piazza del Campo, now regarded as one of the most beautiful civic spaces in Europe, grew in importance as the centre of secular life. New streets were constructed leading to it, and it served as the site of the market and the location of various sporting events (perhaps better thought of as riots, in the fashion of the Florentine football matches that are still practised to this day). A wall was constructed in 1194 at the current site of the Palazzo Pubblico to stop soil erosion, an indication of how important the area was becoming as a civic space.

Medieval coin from Siena (12th century)

In the early 12th century a self-governing commune replaced the earlier aristocratic government. The consuls who governed the republic slowly became more inclusive of the poblani, or common people, and the commune increased its territory as the surrounding feudal nobles in their fortified castles submitted to the urban power. Siena's republic, struggling internally between nobles and the popular party, usually worked in political opposition to its great rival, Florence, and was in the 13th century predominantly Ghibelline in opposition to Florence's Guelph position (this conflict formed the backdrop for some of Dante's Commedia).

On 4 September 1260 the Sienese Ghibellines, supported by the forces of King Manfred of Sicily, defeated the Florentine Guelphs in the Battle of Montaperti. Before the battle, the Sienese army of around 20,000 faced a much larger Florentine army of around 33,000. Prior to the battle, the entire city was dedicated to the Virgin Mary (this was done several times in the city's history, most recently in 1944 to guard the city from Allied bombs). The man given command of Siena for the duration of the war, Bonaguida Lucari, walked barefoot and bareheaded, a halter around his neck, to the Duomo. Leading a procession composed of all the city's residents, he was met by all the clergy. Lucari and the bishop embraced to show the unity of church and state, then Lucari formally gave the city and contrade to the Virgin. Legend has it that a thick white cloud descended on the battlefield, giving the Sienese cover and aiding their attack. The reality was that the Florentine army launched several fruitless attacks against the Sienese army during the day, then when the Sienese army countered with their own offensive, traitors within the Florentine army killed the standard bearer and in the resulting chaos, the Florentine army broke up and fled the battlefield. Almost half the Florentine army (some 15,000 men) were killed as a result. So crushing was the defeat that even today if the two cities meet in any sporting event, the Sienese supporters are likely to exhort their Florentine counterparts to “Remember Montaperti!”.

The historic centre dominated by the Duomo

The limits on the Roman town, were the earliest known walls to the city. During the 10th and 11th centuries, the town grew to the east and later to the north, in what is now the Camollia district. Walls were built to totally surround the city, and a second set was finished by the end of the 13th century. Much of these walls still exist today.[3]