Established in 1822, during the British rule, hence the "Royal", the gardens are set in a horseshoe-shaped curve of the longest river in Sri Lanka, the Mahaweli. The gardens occupy about 150 acres, (60 hectares), with views of mountains to the south and jungle-covered hillside to the north. The garden complex is divided into several different zones, each specializing in one particular genre of flora. There are, roses, ferns, spices, medicinal plants and herbs, green houses of full of orchids, foliage plants, cacti and succulents, among others. Along the river's edge grow masses of giant bamboo, both green and orange, which keep the river from claiming some of the land during floods.