Royal Botanic Gardens, Peradeniya are about 5.5 km to the west of the city of Kandy in the Central Province of Sri Lanka. It attracts 2 million visitors annually. It is near the Mahaweli River (the longest in Sri Lanka). It is renowned for its collection of orchids. The garden includes more than 4000 species of plants, including orchids, spices, medicinal plants and palm trees. Attached to it is the National Herbarium of Sri Lanka. The total area of the botanical garden is 147 acres (0.59 km2), at 460 meters above sea level, and with a 200-day annual rainfall. It is managed by the Division of National Botanic Gardens of the Department of Agriculture.