The San Niccolò complex, which includes the church and adjacent convent, is in the center of the historical town center near Via Elladio. Construction began in 1304 by the Augustinian monks on a site where private homes and two other churches previously stood – a primitive church from the 4th century dedicated to San Niccolò of Bari and one dedicated to San Massimo. The new complex was built in monumental forms – the large church having a single nave, characterized architecturally by vertical development. The convent housed a lavish, well-stocked library of humanistic texts which became a very important place frequented by the greatest scholars of the time, among whom Martin Luther, who stayed there in 1512.
The façade of the church is very simple, with a double slanted roof and a single entrance door in Gothic style, decorated with a frescoed lunette representing the Madonna between Saints Agostino and Nicola, dated to 1412 and attributed to a painter conventionally called “Maestro della Dormitio of Terni. ”
The convent is beautified by two cloisters: one from the 1300s built out of pink and white stone with round arches on pillars, and the other from later in the 15th century, which has two orders of smaller terracotta columns. The arcades of the cloister enclose a large courtyard with two stone sculptures by Anna Mahler: A Woman Drinking and Woman Observing the Sun. A strong earthquake destroyed the complex in 1767 and it fell into disuse. For years it was used as a storage area and improvised shelter until it was renovated in modern times during the 1960s. The building is now used as a congress center, for exhibitions and cultural events of various kinds.