Located at the height of about 1350 metres, there are three Plains which
cover a surface of 15 square km: the Pian Grande (province of Perugia), the
Pian Piccolo (province of Perugia) and the Pian Perduto (province of
Macerata). The Pian Grande, that extends for about 7 km with an average
width of 3 km and a height between 1300 and 1252, is the major Italian
karstic plateau, after the Piana del Fucino and is entirely surrounded by
the ridges of Sibillini Mountains. The origin of the basin is due to the
lowering of the underlying rock masses, in contrast with the lifts that gave
origin to the ridge of Mount Vettore. The main karst morphologies are
represented by various bowl-shaped sinkholes, with waterproof bottom and
supplied with water for many months in the year, funnel-shaped sinkholes
with A waterproof bottom and especially the Ditch of Mergani, a grain-shaped
sinkhole where rain waters end up. What makes the
Plains famous is the Flowering that, between May and June, fills all the
area with poppies, cornflowers, marguerites and lentils and is an unforgettable sight.