The first church dates back to the 13th century and was built in Romanesque style by the Augustinian friars who dedicated it to the Trinity. The Order of the Augustinians was born in Tuscia at that time from the union of eremite communities and in 1244 under the influence of Pope Innocent IV it was officially recognised for the first time in Rome.
The church of the Trinity of Viterbo was consecrated in 1258 by Pope Alexander IV as reported in a plaque in the cloister. Its second name of Sanctuary of the Madonna Liberatrice is due to a miraculous event that took place in 1320: it was May 28 when, in the suddenly dark sky, demons appeared in the form of crows, eagles and bats. The frightened population saw at a certain point the image of the Madonna appear, which had the appearance of that of a fresco that was found in the church of the Holy Trinity, and chased away the evil. The Madonna asked the citizens to pray to her in the church and since then she has been invoked by the Viterbesi, every time they feel threatened and from 1344 on Pentecost Monday there is a procession (today moved to the last Sunday in May).
The fresco of the Madonna and Child by the itinerant painters Gregorio and Donato d’Arezzo is protected by a shrine in a right side chapel.
The church was then destroyed by a fire and had its first reconstruction thanks to Pope Martino V Colonna in 1421. But the late Baroque-neoclassical style comes from the extensions of 1727 by the architect Giovan Battista Gazzale who also modified the orientation of the building.
The façade is made harmonious by a play of colours between the brick-red plaster and the decorations in gray peperino stone and is divided into two levels distinguished by columns in different style. 4 niches then exalt the figures of saints: the niches with Saint Augustine and Saint Thomas of Villanova in the lower part near the main door and the female ones of Saint Rita of Cascia and Santa Monica in the upper part. All the statues were made by Camillo and Vincenzo Pacetti, while at the centre of the church there is a balcony with the symbol of the Trinity in white travertine.
The interior appears in a late neoclassical style enriched with polychrome friezes and marbles with three naves and a cross plan surmounted by a dome frescoed with the scolars of the Church among whom is Saint Augostine, illuminated by 8 recesses.
Among the other works of art we note the funeral monument to Cardinal Raimondo Perrault of 1505, a basin from the 1600s and paintings of the XVI, XVII and XVIII centuries.
But the true work of art is the Renaissance cloister of 1513 spread over two floors with a central fountain in peperino and enriched by 36 columns. On the lunettes of the inner walls of the cloister at the cross vaults and the openings of the cloister, it is possible to admire a pictorial cycle that tells the whole life of Saint Augustine. 44 works created by the Roman painter Marzio Ganassini and by Giacomo Cordelli from Viterbo. The works were made thanks to a legacy of Giacomo Nisini, knight and nobleman, whose coat of arms is found in the cloister.