Perocchè come in su la cerchia tonda
Monte Reggion di torri si corona,
Così la proda, che’l pozzo circonda, ...
- DANTE Inferno C. XXXI -
 

The town was built by the Senese between the years 1213-1219, on a hillock dominating and overlooking the Cassia Rute. Its strategic position facilitated the control of the Elsa and the Staggia Valleys in direction in Florence, the historic enemy of Siena, which at that time was rapidly expanding its territory.
Monteriggioni is without doubt one of the most classical and best known Italian walled towns. During the Middle Ages, its considerable fame led the esteemed poet Dante to refer to its ’round enclosure’ in the Divine Comedy (Hell, chant XXXI vv. 40-41).

The walls, which are nearly intact, cover a length of 570 metres and are alternated by 14 towers and two gates. Porta Franca facing Siena and the Porta San Giovanni towards Florence. These structures were heavily fortified to enable secure access points. The hill on which Monteriggioni rises is natural, even if it seems like a large ‘motte’ (from the name of the classical Norman ‘Motte-and-Bailey’ castles-enclosures built on artificial hills.). The almost perfectly circular layout of the walls was achieved by simply by following the ground s contours. 

The military building work appears physically distinguished from the inhabited area, which, although confined within, was set apart due to the concept of a territory of respect. In medieval times the inhabited area was more extensive than today and consequently had a narrower band of separation. Today the suburbs are essentially authentic. 

The only changes to its structure occurred in the earlier years of the 16th century when, in response to developments in weaponry, the towers were lowered and earth was accumulated at the base of the walls to create a bastion.