Valle de los Ingenios, also referred to as Valley de los Ingenios or Valley of the Sugar Mills, is a collection of three neighbouring valleys located 12 kilometers away from Trinidad, Cuba. From the late 18th century until the late 19th century, these three valleys, San Luis, Santa Rosa, and Meyer, were bustling with sugar production, with more than fifty sugar cane mills in operation and over 30,000 slaves employed by the mills and the plantations that surrounded them. In 1988, Valle de los Ingenios and Trinidad were declared a World Heritage Site by UNESCO to commemorate the former sugar industry. This area encompasses 270 km2 (100 sq mi), including the sites of more than 70 former sugar mills.