Piazza Maggiore (Piâza Mażåur in the Bolognese language) is a central square in Bologna, region of Emilia-Romagna, Italy, largely preserving its 15th century layout. The Northwest corner opens into Piazza del Nettuno with its Fontana del Nettuno, while the Northeast corner opens into the narrower Piazza Re Enzo, running along the flanks of the Palazzo Re Enzo that merges with the Palazzo del Podestà. Flanking the Piazza del Nettuno is the Biblioteca Salaborsa. The Basilica of San Petronio is a minor basilica and church of the Archdiocese of Bologna located in Bologna, Emilia Romagna, northern Italy. It dominates Piazza Maggiore. The basilica is dedicated to the patron saint of the city, Saint Petronius, who was the bishop of Bologna in the fifth century. Construction began in 1390 and its main facade has remained unfinished since. The building was transferred from the city to the diocese in 1929; Palazzo Re Enzo is a palace located on Piazza del Nettuno, in the historic center of Bologna, northern Italy.