The UNESCO World Heritage Site Valle de los Ingenios, or Valley of the Sugar Mills, is a series of three valleys near the city of Trinidad de Cuba. The valleys were the center of sugar cane production from the late 18th century until the late 19th century. At the peak of the sugar cane industry in Cuba, there were more than fifty mills operating in the valleys, with over 30,000 slaves working in the mills and the surrounding plantations. Sugar production was an important industry for Cuba from the earliest settlement by the Spanish, who introduced the crop to the island in 1512. The island became the world’s foremost producer of sugar during the late 18th and 19th centuries.