A private islan is a privately owned island. Privately owned islands exist all over the world, and many can be bought. There are many thousands of uninhabited islands in the world with potential for commercial development of tourist resorts or private recreational use. Commercial development of uninhabited islands can bring up ecological concerns, as many have a fragile environment. Some islands can be bought undeveloped, while other include roads and/or houses. Some celebrities like Diana Ross, Tony Curtis and Claudia Schiffer own their own private islands. Many cruise lines own private islands, such as Castaway Cay, which serve as exclusive ports of call for their ships. Others, like Mustique are owned by resort companies which fill them with hotels and leased villas.