 In the central apse is a Gothic portal leading to the crypt (with a nave and four aisles - originally only two aisles) which has the same surface of the upper church and is decorated by frescoes attributed to the Master of Offida.The upper church, with a single hall, has Giottoesque frescoes, some attributed to the Master of Offida (one is dated 1367 and others to Giacomo da Campli (16th century).Some of the original decorations are much ruined or lost at all.