Situated in the locality of La Canonica, today a heavily wooded area, is a natural terrace delimited by a ditch, on which stand the remains of the ecclesiastical structure of San Niccolò.

An investigation of the published written sources in the State Archive at Siena found what to date is the earliest attestation. This is a document of 1137 regarding the sale of assets by the bishop of Volterra to the bishop of Siena. The canonical church of San Niccolò was not amongst the assets sold to the diocese of Siena, however the silver mines situated close to San Niccolò were ceded to Siena.
Therefore, this documents attests the probable role played by the canonical church itself in the silver extraction and management of its working, on a par with the local nobility which controlled the production processes.

Topographical investigations carried out in the municipality of Montieri by the University of Siena at the beginning of the 1990s, as part of an undergraduate project coordinated by Riccardo Francovich, highlighted the presence on the site of galena, sphalerite and calcopyrite as well as waste products from metal working processes. On the site’s surface the walls of a church built of small limestone blocks were visible. The main nave and at least two apses were identified. Around the church structure there were several buildings which cannot be definitively identified at present due to the presence of trees. Moreover, in some of the areas adjacent to the site there were dumps of waste materials from the working of coinable metal.

In the Middle Ages the territory of the municipality of Montieri was of historical importance due to the presence of the silver mines. The first certain document regarding Montieri mentions the donation made in 973 by Lamberto, son of the Marquise Ildebrando of the Aldobrandeschi counts, to the canonico Ropprado, drawn up in the castle of Gagliani in the municipality of Campagnatico. This act, in which part of the \“corte et castello sito Monterii\” was donated to the church of Volterra, also attests the transformation of Montieri into a castrum as early as the 9th century. In the same century a rural structure named after San Paolo was attested as being built in a place circa two kilometres south-east of the present town of Montieri.

Between the 11th and 13th century there was a period of increased exploitation of the mineral resources in the territory of Montieri. In the town itself major changes occurred, with the foundation of a church dedicated to San Giacomo, the construction of the fortification, of several aristocratic palaces and the municipal foundry. During the 14th century the silver mines were gradually exhausted and were ceded to Siena.

The study of the Canonica of San Niccolò is one of the many activities that are part of the University of Siena’s long running study of settlement dynamics in the territory of the Colline Metallifere. These include survey, excavation of fortified settlements and the mapping of mining areas. The main aim of these investigations is the study of the birth of the medieval settlement network, in relation to the exploitation of the mineral resources and control of metallurgy production processes.