The front facade was rebuilt in 1891 after the original one collapsed. It is of striped marble and stone with open arches that have lace detailing not commonly found in Italian sacred architecture while the tiled cupola is quite common amongst churches of the area. The tympanum's mosaics portray “The triumph of Christ” in a work created by Domenico Morelli and whose original designs are retained in the Town Hall.
A wooden 13th century Crucifix hangs in the liturgical area. Another crucifix, made of mother-of-pearl, was brought from the Holy Land and is located to the right of the back door.
The High Altar in the central nave is formed from the sarcophagus of the Archbishop Pietro Capuano (died 1214). Above the altar is a painting by Andrea dell'Asta of The Martyrdom of St. Andrew.
Sixty-two steps, wide and steep, lead up to the doors. Cast in Constantinople before 1066, and signed by Simeon of Syria, the cathedral's bronze doors are the earliest in Italy of post-Roman manufacture. Begun in 1180, and completed over 100 years later, the Romanesque style bell tower is off-center.