The massive church honoring Bologna’s patron, the 5th-century bishop Petronio, was begun in 1390, designed to be larger than St. Peter’s in Rome. Papal powers cut off funding to protect their status and the basilica remains unfinished—the formidable brick walls were never sheathed in marble as intended and transepts are severely truncated (look down either side of the church to see where extensions end abruptly in the surrounding streets). Among the few flourishes are a magnificent central doorway surrounded by Old Testament figures rendered in marble by Jacopo della Quercia of Siena. The artist was in his fifties and well regarded when he came to Bologna in 1425 to undertake the commission; he finished just before his death in 1438, leaving a legacy that influenced many of the great artists of the Renaissance. Among them was Michelangelo, who claimed that della Quercia’s rendering of the Creation of Adam here was the inspiration for his Genesis in the Sistine Chapel. In the Cappella Bolognini, the fourth on the left as you enter, Giovanni da Modena painted a fresco cycle between 1408 and 1420 that depicts scenes from the life of Petronio, along with scenes of Hell from Dante’s Inferno—with a startling depiction of Satan eating and excreting doomed souls and Mohammed being devoured by devils in Hell (Al-Qaida operatives and other terrorists have twice in recent years tried to blow up the church in retaliation for the alleged defamation). The rather stark interior is enlivened ever so slightly at noon when a shadow indicating the day of the year makes an appearance on a meridian line in the left aisle; designed by Bologna’s famous 17th-century astronomer Giovanni Domenico Cassini, the longest sundial in the world stretches for 70 meters (231 feet).