The Basilica of San Petronio is the largest church in Bologna. It dominates the Piazza Maggiore and, despite being largely unfinished, it is one of the most extensive churches in Europe. Its imposing dimensions (132 meters long and 60 in width, with a height of 44.27 meters) makes it the fourth-largest church of Italy. In the Basilica of San Petronio, it is impossible not to know what time it is. In place of a clock though, the structure houses the longest sundial in the world. It measures 67 meters and crosses the floor of the church since 1657. It was Domenico Cassini who made it; a professor of astronomy, who believed that the motion of the planets depended on the sun.  With this guided tour, discover the beauty and history of this church. Afterwards, take the elevator to the magical panoramic terrace and relish in city views as far as you can see.