It would be sufficient to mention two names to persuade you to visit this splendid example of Romanesque: Antonio Allegri called Correggio and Benedetto Antelami.
The Latin cross cathedral is imposing, rich in the side chapels, gorgeous in the dome and beams of lights get into the windows, emphasizing the frescoes that cover the walls.
To render the visit more exciting, two passionate musicians went on playing the great organ and for this additional charm we have to thank them.

A short history:
After the destruction of the early Christian church, in 9th century the bishop Guidobo ordered the rebuilding.
In 1055 or 1058 a fire probably destroyed the ancient church.
The new reconstruction, due to the bishop Cadalo, ended in 1074.
Consecrated in 1106 by the pope Pasquale II, in 1178 the front was completed and the whole building was revised by Benedetto Antelami.
Between 1284 and 1291 Obizzo Sanvitale rebuilt the bell tower, which on 21-22 October 2009 was damaged by a lightning and the reparation works ended in 2015.

For more info:
wikipedia: Duomo di Parma
www.piazzaduomoparma.com/en: cattedrale