The cathedral of Cagliari was built in the 13th century, during the time Pisa ruled the island, so its original style was Pisan Romanesque. Over the years, the church was redesigned, but parts inside still reflect its Pisan past. A good example is the 12th-century pulpit, which was given to the church as a gift from the rulers of Pisa.

Beneath the cathedral is a crypt (also called a Santuario – a place of worship) from the 17th century, richly decorated. On its walls are urn-like containers holding the ashes of 179 Christian martyrs.