The church of St. Ephisius stands on a cave, which sinks nine meters into the limestone rock, traditionally believed to be the prison where Ephisius was imprisoned before being beheaded on the beach of Nora in 303 A.D.
In 1726, the building of the Oratory of the Archconfraternity was erected according to the design of Piedmontese architect Antonio Felice De Vincenti. Later the building was modified to conform to the more modern Piedmontese Baroque style; in 1780 the old church was demolished, and its reconstruction was completed in 1782. The high altar, in precious polychrome marble by Lombard marble worker Giovanni Battista Franco, is dated 1786; while the altar in the chapel of St. Ephisius, on the right, is from 1791. The statue of the saint, by a still unknown author, is placed here, and is carried in procession every year on the occasion of the famous May 1 festival.
The ancient sacristy houses the processional statue of the Lonis, dating from 1759. In 1798 the altar of the Crucifix was erected in the Oratory of the Archconfraternity, which was attached to the church in the late 19th century. The interior contains paintings by Francesco Costa, Domenico Colombino and Sebastiano Scaleta of Cagliari.
Among the valuable statues is a 17th-century sculpture of Neapolitan ambit depicting Ecce Homo.
Access to the crypt is via a steep staircase carved into the rock, traditionally the prison of Efisiu gloriosu. In Roman times the hypogeum was possibly used as a temple of the goddess Isis. A well in the center of the floor would have contained water for initiation rites. In 1616 a tomb was discovered with a skeleton attributed to St. Edizio. Confirmation came from a marble slab on which was written bonae memoriae Editius.
