The Cathedral of San Nicola is the centrepiece of Sassari's old town, a 13th-century church with a spectacular Spanish Baroque facade added in the 17th and 18th centuries. The facade is one of the finest examples of Spanish colonial Baroque architecture in Sardinia — an exuberant mass of carved stone saints, angels, and ornament that looks more like it belongs in Mexico City than in a Sardinian provincial capital.
The interior is Gothic and contains some good works of art, including a 14th-century silver crucifix and several notable paintings. The church faces onto a small piazza in the heart of the old town, and the contrast between the elaborate facade and the plain grey stone buildings surrounding it is striking.