The journey through the city’s magic secrets starts from the Basilica of St. Petronio, whose geometrical shape recalls a symbolism dear to the master masons. The paving in the interior houses a meridian line which revolutionised the calendar. The façade was built according to Astrology. Architectural balance is obtained by inscribing an equilateral triangle (a symbol of elevation), a square (which suggests a sense of stability) and a hexagon (which refers to man and completion) in a circle. These basic geometric forms mark twelve invisible dots outside the circle, which determine the height and volume of the church and remind of the never-ending circle of the zodiac. For those who love their hidden treasures, the legend says that one is buried behind one of the three thousand flowers carved in the façade of Palazzo del Podestà. In the close-by via Gargiolari, a closed door hides the studio of the famous physician and astrologer Cecco D’Ascoli who was burnt at the stake.