Not to be missed in Chianni is the underground church of the Compagnia della SS. Annunziata, established by the inhabitants, which boasts a crypt located under the church of S. Donato. The building, which is completely underground, was probably built during the extension works of the parish church in the early 18th century.
Its importance is due to the decorations covering both the large barrel vault of the roof and the side walls. This is a cycle of frescoes painted by the Pisan Giovanni Battista Tempesti in 1739. The vault depicts the Eternity, the Nativity of Christ and the Assumption of the Virgin. In the corners of the central episode are the figures, painted in monochrome, of the four prophets, Isaiah, Habakkuk, David and Michaea. On the altar, dating from 1750, the statues of the Announcing Angel and the Virgin Annunciate, in plaster painted in enamel.
The church is used for parish activities and theatre performances.