Some historians believe it was built over the “Sacrum Verticem” of the Umbrian-Roman town, where in the past, a temple rose dedicated to the Sun God. Since the 6th century, it became a place of worship dedicated to St. Lawrence, a name that was chosen because it recalled the original Cathedral, known as St. Lawrence in Urbestole, situated outside the city walls, along the ancient layout of the Via Amerina (now it is the back road Amelia-Orte). It was consecrated to St. Firmina by will of Bishop Paschalis during the 9th century, who moved the bodies of the martyred Saints, Firmina and Olimpiade, found near the Castle of Agoliano (that is the current Lugnano in Teverina according to some scholars), and the relics of St.Imerio, a legendary 6th century Bishop of Amelia. The original building had a presbytery over the nave and a crypt below containing relics of Amelia’s two Patron Martyr Saints.

In 1220, after a fire or an earthquake had occurred, the Cathedral was rebuilt reflecting the Romanesque architectural design choice. When the Imperial Army of Frederick II occupied Amelia in 1240, the entire religious complex suffered terrible damage and in 1255 restoration works begun. An enlargement intervention took place in 1323-24 when new lateral chapels were built into the church, while the wooden choir pews were commissioned in 1411. During later centuries, the church remained unchanged until the night between the 19th and 20th December 1629 when a brazier was left alight by a careless organist and a burning ember fell out and set fire to it, almost totally destroying the right section of the nave. Between 1636 and 1677, radical restoration works began, considerably altering the appearance of the whole building by lowering the level of the nave and doing away with the crypt. A new choir and a new main altar were built and the bodies of St. Firmina and St. Olimpiade were placed below it. The facade remained unfinished until 1887.

The church interior is now characterized by remarkable decorations executed by the purist painter Luigi Fontana during the same year and he was alos appointed to execute numerous frescoes that decorated the ceiling of the central nave, the elliptical dome and the underlying plumes and the two lateral transept domes. The Cathedral conserves numerous works of art belonging to various ages that are the witnesses of its story: to the right of the Cathedral entrance, there is a small marble column that is supposed to be the one to which St.Firmina was tied while she was undergoing her martyrdom. The tomb slab of the Bishop Ruggero Mandosi, a work of art belonging to Agostino di Duccio studio, is walled up in the first chapel. The second chapel to the right belonged to the Farrattini family (cross reference to panel nr. 5).

 The entrance leading into this chapel houses two war trophies (standards that are supposed to be stolen from the Turks during the famous “Battle of Lepanto” in 1571). Over this chapel’s altar hangs an important painting, an early work by Federico Zuccari (Sant’Angelo in Vado, 1539 – Ancona, 20 luglio 1609), and to its sides there are two funeral monuments of Bartolomeo II and Baldo Farrattini by Giovanni Antonio Dosio and Ippolito Scalza. Located in the chapel situated in the right transept is a big panel representing The Last Supper, painted in 1538 by Giovan Francesco Perini (Amelia, born before 1523 – died after 1574), who worked in Rome, in the Vatican, during the years of Raphael and his studio. In the middle of the left transept altar in baroque structure, is located a precious 15th century panel by the anonymous Master of Assumption of Amelia. It is a work of art to which the popular devotion recognised the miracle of the rescued from danger from the terrible earthquake of 1703: for this reason the work of art is put on display only in August.

In the first chapel on the right side we can admire a 15th century baptismal font and a statue of St. John the Baptist, inspired by Donatello sculptures, is on the top; in the same chapel, inside a recess on the right wall, the sepulchre of the Bishop Giovanni Geraldini is inserted, above which is located a very refined low relief (Madonna with the Child and three allegorical pictures of the Virtues contemplating the Baptist) by the Renaissance sculptor, Agostino di Duccio, who was working in Amelia on behalf of the Geraldini also in the family chapel in the Church of St.Francis. The diocesan collection, housed inside the rooms near the Cathedral, also conserve the works of art by Antoniazzo Romano, Giovan Francesco Perini, Bartolomeo Barbiani among others.