Cilaos is a town and commune on the French island of Réunion in the Indian Ocean. It is located centrally on the island, in a caldera of altit…Cilaos is a town and commune on the French island of Réunion in the Indian Ocean. It is located centrally on the island, in a caldera of altitude 1,214 m. The caldera is also named for the community. The name Cilaos comes from the Malagasy word, Tsilaosa, which means the place one does not abandon.