This imposing basilica consecrated in 1253 marks the Franciscan movement led by Brother Elius, who was responsible for its construction, towards architectural splendour and decoration. The church comprises a sober and bulky lower basilica decorated with frescoes (by Simone Martini) and a tall and slender upper basilica which is an accomplished piece of Gothic architecture. The latter is decorated with an admirable cycle of paintings by Giotto depicting the life of St Francis.