Piazza del Campo is a unique place in the whole of the world, starting with the very particular conformation of the ground, which turns the square into a big concave shell. The paving is made of red bricks arranged in fishbone style, divided into a sunburst pattern by nine strips of travertine (in memory of the Government of the Nine, who ruled over the city from 1292 to 1355). The white marble of the Fonte Gaia stands out on the paving, it is the masterpiece of 1419 by Jacopo della Quercia, later replaced by a copy. There is also the Palazzo Comunale (town hall), unusually built on the lowest part of the square, and also the tall, slender Torre del Mangia that stands out against the sky (it reaches 102 metres including the lightning conductor). At the base of the Palazzo is the Chapel of the Virgin, or Chapel of the Square, constructed and voted for by the Sienese, after the end of the terrible plague of 1348. And surrounding the chapel are the elegant façades of the Palazzi Signorili, belonging to the wealthiest of families: the Sansedoni, the Piccolomini, and the Saracini.