The bay of Armação de Pêra is a broad bay bordered by cliffs made of calcarenite, which have remained in a dynamic equilibrium with sediment supply for the past 3,300 years. The cliffs expose Miocene fossiliferous limestones from the Lagos-Portimão Formation and contribute a small amount of sediment to nourish the beach, particularly during periods of erosion. This bay is one of the few stretches of stable coastline in the western Algarve, where sand accumulates to form a continuous beach that extends approximately 6 kilometres.