The patron saint of Costarainera is Saint John the Baptist, celebrated on 24 June. The parish church dedicated to him, in the main village, has an unusual elliptical shape and was built in the 18th century: it holds a number of sculptural works, including the Baptism of Christ and the Madonna.
The municipal territory also holds the church of Sant'Antonio Abate, from the 12th or 13th century, which once held the painting of Saint Sebastian and Saint Lucy by the painter Emanuele Macario da Pigna, today kept in the town hall. Along the road to the hamlet of Lingueglietta stands instead the church of San Sebastiano, from the 15th century, hidden among the olive trees: the two-nave structure also holds among the religious symbols carved into its column capitals the noble coat of arms of the Lengueglia family. From the highest point of the Paorelli district, where an old watchtower stands, the clear winter mornings offer views of Corsica, the mountains of Tuscany and Provence.
