The Valle del Mercure is a large river basin, located in the southern part of Lucania and in the northern part of Calabria, which was occupied by a Pliocene Lake. In the Valle del Mercure, around the year 1000, in the towns of Castelluccio Inferiore, Laino Borgo, Laino Castello, Mormanno and Viggianello settled community of monks, differently organized monastic life or as a hermit in the numerous caves, which gave rise to one of the most important religious communities of the time called Mercurion, from which in fact the names of the Valley and the river. Among the most important members cited San Nilo da Rossano, founder of the Abbey of Grottaferrata. In the Lombard period the whole valley was part of the castaldato of Labrador.