This small lake amazes for its dizzying depth (up to 13.5–15 m, second only to Altofonte among Sicily’s natural lakes) and for its cobalt-green colour, reflecting the overhanging white gypsum cliffs. The lake was born on a November night in 1907, when the karstic action of underground waters dissolved Miocene gypsum banks, causing the ground to collapse. The event, described by the scholar Marquis Achille De Gregorio in Il Naturalista Siciliano, swallowed the bed of an old vineyard and created a circular sinkhole with walls up to thirty metres high.
Fed by deep aquifers and lacking outlets, the basin maintains a constant water level even in summer, favouring the bloom of helophytes and water lilies and offering a haven for coots, mallards, kingfishers, and the rare little grebe. Among the reed beds thrive tamarisks and yellow flag irises, while on the clay banks delicate Ophrys orchids bloom. Established in 1997 (13.13 ha) and entrusted to Legambiente, the reserve protects a geosite of international value: the natural outcrops display, like an open-air stratigraphy manual, the alternation of brackish clays, selenitic gypsum, and yellowish marls that recount the Messinian salinity crisis of the Mediterranean.
A comfortable 2.5 km dirt trail starts from the SP 42 and reaches the rim of the crater, offering breathtaking views over the Imera valley and the Madonie mountains. Inside, however, there are no water points or services: trekking shoes, a hat, and mandatory booking for guided tours are required (tel. +39 0934 564038; lagosfondato@legambienteriserve.it
). At sunset, the grazing light ignites the gypsum walls and turns the lake into an emerald set in rock, providing a spectacular setting for birdwatching and for reflecting on the fragile balance between karst nature, surrounding agriculture, and environmental protection that makes Lago Sfondato a small yet precious laboratory of geology and biodiversity in the heart of Sicily.