Located on the top of the Polvese Island, built with blocks of limestone, sandstone and travertine, it is considered a fundamental point of reference for the knowledge of the early Umbrian Romanesque. The façade has a central rose window with a sandstone frame and two pairs of superimposed windows in correspondence with the side aisles. The square-based bell tower rises outside the church and was originally supposed to be cuspidated.

The Benedictine Monastery of the Olivetani, built perpendicular to the Church of San Secondo, housed on the ground floor the refectory and the Chapter Hall with three large ogival windows, while on the upper floor, communicating with the church, there were the monks’ cells.

Definitely abandoned at the beginning of the eighteenth century due to the swamping of the area, the entire complex has been the subject of a recent architectural recovery according to eco-compatible methods and is now home to an environmental education study center. The remains of some monks found during the renovation work now lie inside the crypt.