The lake of Prà di Lama It is the only lake of natural origin in Garfagnna, fed by underwater springs, with a flow rate of about 120 l/sec and a temperature of 30 ° C. This lake has fueled fears and legends of all kinds among the inhabitants of Pieve Fosciana for centuries. A magical lake that appears suddenly, closes up until it disappears and reappears again amid roars and puffs of gas. Miraculous and healing waters that flow in its vicinity, but also poisonous gases that brought epidemics. It is actually a phenomenon that is well known and studied today, the formation of an almost circular depression due to a sudden collapse of the ground (sinkhole). This is its recent history: on August 15, 1828, at 11am, a series of roars preceded a sinking, with gas emissions and mud leaks; thus a small lake with a diameter of 40 m, depth 11 m was formed, in the place of the meadows which housed a thermal spring equipped for therapeutic purposes. In 1842 the lake was almost completely closed.

Between February and March 1843 other sinking led to the enlargement of the lake with the formation of another 10 springs: the inflow of mud into the Serchio River was visible for about 25 km.

Once again at the end of the Second World War the Prà di Lama lake was a small pond, then further sinking restored the cavity. Currently the lake has a diameter of a few hundred meters, the level is subject to sudden drops; recent collapses have affected the banks up to the road, interrupting access to the source whose sulphurous-radioactive waters come out at a temperature of 37° C. and are considered almost miraculous by the inhabitants of the area.