The Monza Cathedral, dedicated to John the Baptist, was built in 1300 and is located in Piazza del Duomo. Its charming façade combines multiple colors, windows, and spires, reflecting the transitional architectural style between Romanesque and Gothic periods. Adjacent to the cathedral stands the bell tower, which reaches a height of 80 meters.

Inside, the church is rich in Baroque paintings, and the organ dates back to the Renaissance period. The highlight is the iron crown, which contains a nail traditionally believed to be one of those used in the Crucifixion of Jesus.

Equally impressive and significant is the chapel to the left of the main altar—the Chapel of Princess Theodolinda, who was married twice to two Lombard kings (hence the name of the region). The chapel is adorned with several frescoes depicting events from the life of the Lombard people. The princess’s importance is celebrated annually on January 22 in a special ceremony held in her honor.