The medieval village of Monteriggioni is a part of the so-called the Montagnola Senese. The territory has stretches extremely differentiated: it can in fact be easily noted how around the relief of Montemaggio there are some small plains as Pian del Lago and Pian del Casone, Il Canneto, alternating with a series of small valleys formed by rivers and streams that characterize the central part and eastern part of the territory.
The castle of Monteriggioni was built by the Sienese, for order of the podesta Guelfo from Porcari, in a period between 1214 and 1219. The ground, purchased by the noble family from Staggia, was the site of an ancient Lombard farm (the designation of Montis Regis probably indicated a bottom of royal property or that enjoyed tax exemptions from the crown portion). The construction of the castle by the Republic of Siena had mainly defensive purposes, as the village rose on Monte Ala in position of domain and surveillance of the Francigena, to check the valleys of the Elsa and of the Staggia in direction of Florence, historic rival of Siena. The building practically ex novo of a castle was a novelty in the expansionist policy of Siena: previously, in fact, the city had purchased castles already existing. The circular path of the walls was obtained simply by following the trend hill natural. The castle of Monteriggioni was also surrounded by so-called charcoal burners, i.e. moats filled with coal that was burned to repel the assaults.
The plain at the foot of Monteriggioni was occupied by a swamp, on the margins of which faced Monteriggioni and the ancient Abbadia a Isola, that depended on the bishop of Volterra. When the monks of the Abbey began the land reclamation of the marsh digging a tunnel to divert the waters, the senesi filled overnight because the swamp was a natural protection against the armies of enemies. The question went on for a long time, until in 1246 it came to a compromise: the monks ultimarono gallery, and the Senese preserved a substantial area near the castle. Still today, in the plain of the reclaimed, emerges an old tower, located just above the underground gallery: served as a breather and input for the maintenance of the tunnel, which today is no longer viable because blocked by debris.
The core of Monteriggioni is a small fortified village. The diameter of the castle is 172 meters, surrounded by a massive walls of elliptical shape with a thickness of up to 2 meters, interspersed with 15 towers and two ports, which surrounds a hill called Monte Ala. The Towers, today, rise above the walls to 6.5 meters, with a thickness of 4x6 meters, and are visible only 11: the other four were reduced to the level of the walls (were "cimate") the 11 raised were, so to speak, restored in the 1920s, on the occasion of the centenary Dantesque 1921, because visible from the then via the main transit, the Cassia. Above the walls ran a walkway that traveled around the entire perimeter. In 2005 were rebuilt some parts of the walkway, from which you can enjoy a unique view and suggestive. The Porta Franca or Romea (oriented toward Siena) rises at the base of a tower while that toward Florence, bears underneath, opens in the wall and is next to one of the towers of the fortified perimeter. Entering from Porta Franca or Romea, which originally was equipped with a heavy railing which was lowered in the event of danger, you enter Piazza Roma, the heart of the village. The square was originally "a sterro" (without flooring), but was paved in the seventies with stone from the quarries of Rosia (said stone from Torre). Today the square is surrounded by gardens and orchards, very important in the past to allow the survival of the population even in case of siege. The square is overlooked by the Church of Santa Maria Assunta.
One of the oldest towns of the territory is that of Abbadia a Isola, beyond Abbadia you can visit Strove, an ancient village of Little back to the VI century with a precious Pieve a hut. Inside the former marshes of the Canneto and near scanty is located a etruscan necropolis dating back to the IV century B.C. Other places of remarkable importance are the fourteenth-century castle of the nut and the villa of Santa Colomba that, on horseback between the fifteenth and sixteenth century, was the residence of the lord of Siena Pandolfo Petrucci.