Siena is said to have been founded by the two sons of Remus, it is said that after he was murdered by his brother Romulus the two boys fled Rome on black and white horses, which is why today the city flag is black and white. There are many references to the boys within the city including statues for the she wolf protecting both Romulus and Remus as infants.
Siena is a UNESCO World Heritage Site. It is know for the Palio which is run every July and every August around the Piazza Del Campo. It is a beautiful city to visit.
Places nearby to visit are San Galgano and Monteriggione.
The legend is that San Galgano retired here and lived as a hermit. He thrust his sword in a stone to show he wanted to live in peace. Today you can still see the sword embedded in the stone, rather like King Arthur's Excaliber, no one has been able to draw it out of the stone. Today it is an abbey in ruins, however a number of concerts are held here every year.
Monteriggione was an outpost to protect Siena during it's time as a city state. It is a castle or a castellated town. It has a number of towers. I understand the TV series Game of Thrones featured this. Monteriggione is on the Via Francigena, which was the ancient pilgrim's road from Canterbury to Rome.
Today it hosts a medieval museum and a number of medieval festivals where everyone dresses in medieval clothes.