The lower order has five rose windows. The central window, which is the largest, is rich in carvings and ornate mosaics and is flanked by the symbols of the four Evangelists.
Below, the Renaissance-style Portico, which was designed by Antonio Barocci, is made of five round arches with Corinthian columns in between.
At the entrance of the Cathedral, the magnificent portal (earlier than 1198) is decorated in Romanesque-style.
The interior of the Church, radically transformed in the early 17th century, is in Baroque style and with a Latin cross plan with three naves of six bays each, a transept, a large semicircular apse and a dome, without tambour.
The nave's mosaic floor of the Romanesque Cathedral is still preserved and it was probably built in the 12th century.
In the niche of the counter façade there is a bronze bust of Urban VIII by Gian Lorenzo Bernini (1640).
A fresco with Madonna and the Saints by Pinturicchio decorates the apse of the first chapel of the right aisle.
In the right transept, within the altar, there is a painting by Annibale Carracci and, on the left wall, the sepulcher of the painter Filippo Lippi (who died in Spoleto in 1469), which was designed by his son Filippino and built by an unknown 16th century Florentine sculptor.
To the right of the presbytery, there is the 16th century chapel of the Most Holy Icon, named for the presence of a 12th century Byzantine tablet, which was donated to the city by Frederick Barbarossa as a "symbol of peace".
The apse is covered by beautiful frescoes (1467-1469) by Filippo Lippi and his assistants, depicting stories of the Madonna.
At the center of the presbytery, the altar by Giuseppe Valadier (1792) is made of polychrome marble and flanked by four tall columns.
Finally, on the left aisle, the Chapel of the Relics still preserves 16th century wooden sculptures and inlays, as well as one of only two extant handwritten letters by St. Francis, addressed to Brother Leone.
The Cathedral is closed in the middle of the day.
Winter season: 8.30am- 6 pm;
Summer season 8.30am-7 pm.