This superb monument was built in 1219 during the city's golden age. The façade, flanked by two slender towers, is embellished by a lively play of colours between the stone and marble; the three arched doorways are adorned with low reliefs attributed to the sculptor Benedetto Antelami. The broader bell tower, on the right side of the church, dates from the 15C. Although the inside is starker, note the inlaid wooden stalls and the 14C tomb of Tommaso Gallo, the basilica's first abbot. The cloisters offer a good view of the complex.