The Via Francigena, which runs through an area rich in holm oaks and oaks, sees the Hermitage of San Leonardo al Lago at Santa Colomba. According to ancient documents, the place was remembered for the presence of a lake that dried up in the 18th century. Archaeological finds, uncovered between 1975 and 1980, brought to light a square cistern and a cave, allowing us to assume that the hermitage was founded before the 12th century. Later, in 1239, the monastery passed to the Augustinians, and in 1250 it was unified with that of San Salvatore di Lecceto, thanks to a papal bull. The presence of prominent religious figures, including the Blessed Agostino Novello, who spent the last years of his life at the hermitage, contributed to making it a place of pilgrimage.
A surrounding wall structure and two towers, one round and the other square, attest to the fact that, in 1366, the hermitage was fortified to defend the surrounding populations from possible conflicts. The architectural evolution of the monastery complex is linked to the early hermits' adherence to the Augustinian order, with buildings organised around a quadrangular cloister. In the 14th century, the extension of the Romanesque church and the construction of the new Gothic church with a single nave, divided into three bays and a rectangular apse, marked a period of great prosperity, supported by donations of land, offerings from the devout and institutional interventions. Between 1360 and 1370, the choir was entirely frescoed by the Sienese painter Lippo Vanni, with a cycle dedicated to the Virgin. On the ground floor, originally used as a refectory, is a valuable fresco depicting the Crucifixion, attributed to Giovanni di Paolo in his youth, around 1445. In 1516 Pope Leo X decreed that eight or nine friars would live there with the allocation of two farms and a vineyard. The convent was suppressed in 1783, but was acquired by the state in 1957.