The conventual complex of St. Agostino was established at the time of the Magna Unio in the area interested by the urban development decreed by the Municipality in 1252. The basilica was erected according to the canons of mendicant architecture and decorated adhering to the figurative ideal of the
Biblia Pauperum. The counter-façade and adjacent walls still retain interesting fragments of the original decoration.
The apse, with its imposing mixtilinear forms, was lightened by Gothic windows, destroyed by the earthquake of 1898 and rearranged in the second half of the 20th century when the basilica obtained the title of parish and systematic interventions of consolidation and restoration (recently completed) were undertaken.
During the seventeenth century, following the post-Tridentine liturgical regeneration dictates, the cloister was erected and the basilical hall renovated through the alignment of the side altars with the cornu Epistulæ and the cornu Evangelii.
The transept was embellished by the side chapels respectively dedicated to St. Rita of Cascia, depicted in the painting of the knight Lattanzio Niccoli, and to The Massacre of the Innocents, depicted in the canvas by the painter Ludovico Carosi da Terni. Here was placed the large fresco of the Crucifixion executed in the mid-fifteenth century by the artist Liberato di Benedetto di Cola di Rainaldo. Once it was hosted in the refectory, later converted to become a gymnasium, when as a result of the post-unification suppressions,
the convent was used as seat of the local Boarding School.