The grottos of Alvados have been discovered in 1964, by a group of workers of the marble stone quarries of the Serra de Candeeiros, whose curiosity was waked up when hearing the delayed fall of stones in a precipice that of course seemed to them to be deep. They prepared one first slope to grottos, equipped with cords and lanterns, and to each other found a succession of rooms of stalactites and estalagmitas, related.