Sierra Bermeja is a mountain range in southwestern Puerto Rico. It covers the area from the Laguna Cartagena to the north, to the Caribbean Sea to the south. From the Boqueron Forest to the west, to La Parguera to the east. It consists of a combination of volcanic rocks, completely crossed by serpentinite and amphibolite faults, which could well be the oldest known rock in Puerto Rico. The mountains were used by the Taíno people as refuge from the Spanish, and then by smugglers during the Spanish colonization.