Key facts

• Palazzo d’Accursio (Palazzo Comunale, 1245-XV sec.): The town hall of Bologna, built on the site of the medieval house of the jurist Accursius (d. 1263) — the most important jurist of the Glossators school, who compiled the Glossa Ordinaria (the standard commentary on Roman law used throughout medieval Europe); the palazzo was enlarged repeatedly from the 13th to the 15th century and now contains the civic collections (Collezioni Comunali d’Arte) on the first floor and the offices of the municipality on the upper floors; the facade has a large crenellated tower (Torre dell’Orologio) with the 1451 astronomical clock by Giovanni Dondi dell’Orologio (a later copy — original mechanisms survive in the Museo della Musica)
• Basilica di San Petronio (1390-incompiuta): The civic basilica of Bologna — the 5th largest church in Europe by interior volume (132 m long, 66 m wide, 45 m tall in the central nave) — was begun in 1390 and is STILL officially unfinished (the terracotta brick facade was completed only to mid-height; the original project called for a marble facing to the height of the nave and two flanking towers that were never built); the facade has three Gothic portals by Jacopo della Quercia (1425-1438 — the most important sculptural programme in Emilia) and the remains of a 1562 astrological meridian line by Egnazio Danti (the longest astrological meridian in Italy, replaced in 1655 by the Cassini meridian still visible in the floor)
• La Meridiana Cassini (1655): The brass meridian line inlaid in the floor of San Petronio (1655, Giovanni Domenico Cassini — the astronomer who later directed the Paris Observatory and discovered the gap in Saturn’s rings) is the most accurate astronomical instrument of the 17th century — 66.8 m long, the longest in Italy; it was used to precisely calculate the length of the solar year and verify the Gregorian calendar reform; it still works and casts a beam of sunlight through a pinhole in the dome on the summer and winter solstices and equinoxes
• Fontana del Nettuno (1566, Giambologna): The large bronze fountain in Piazza Nettuno (adjacent to Piazza Maggiore) was designed by Giambologna (Giovanni da Bologna, 1529-1608) for Cardinal Carlo Borromeo and cast by Zanobi Portigiani in 1566; the Neptune figure (4.5 m tall) was the largest bronze cast in Italy since antiquity at the time; the fountain’s four sirens (pressing their breasts to release water) caused a famous theological controversy — Pope Pius IV demanded that the sirens be clothed, and Giambologna reportedly made the Neptun lean back slightly so that his muscular torso would partially obscure the sirens from the papal viewpoint of the Via Galliera
• UNESCO: 2021, rif. 1650
• GPS: 44.4940, 11.3427 — Google Maps (Piazza Maggiore, Bologna)