The church of San Biagio is the earliest building in Cittiglio: it is a single naved chapel with the altar to the west and bell-tower built inside the façade next to the church’s one entrance.

The first excavation campaign ascertained that the present church is the result of a series of building interventions, some of which radical. The original church, which may date to the early medieval period, was certainly on the opposite alignment to the present one, the altar canonically facing east. Around the year 1000 an important cycle of frescoes was painted in the presbytery area, today these are almost completely lost. However, the excavation brought to light a rare representation of the Chimera which was part of this cycle. A second fresco on the north wall dates to the late Romanesque period. This shows a naïve depiction of a small winged dragon, lying on its back whilst being pierced by the spear of a saintly knight.

At another point during the Romanesque period (second half of the 11th century) a large construction was put up in front of the façade, its width corresponding to that of the Romanesque nave, its depth equal to half of the latter. This was an atrium or exonarthex specifically destined for funerary use where the deposition of the earliest privileged burials began. Of the two investigated so far, buried within the typical stone loculus of anthropomorphic shape, the first belonged to an adolescent, probably female. The second, as well as the residual remains of three previous burials (one infant, an adult male and an adult female), contained the skeleton of an adult male who had been decapitated at a young age.