A private island is a disconnected body of land wholly owned by a private citizen or corporation. Although this exclusivity gives the owner substantial control over the property, private islands remain under the jurisdiction of national and sometimes local governments. Their size vary widely, from that of a typical suburban yard to several hundred square kilometers. Ownership Virtually all islands in the world are claimed and governed by some national government. That nation's laws apply, and any attempt by the owner to claim sovereignty would generally be unrealistic. Nevertheless, some people still try to set up their own micronations on islands, like real-estate millionaire Michael Oliver's attempt at building a libertarian city-state called the Republic of Minerva in the southern Pacific Ocean. There are widely varying government policies regarding private islands: for instance, islands off the coast of China, like any other land within the country, cannot be purchased outright, but only leased from the government for a maximum period of 50 years. "Private" islands in the United Kingdom, Brazil, Chile and some other countries are not legally entirely privateany foreshore, such as a beach, is owned by the government, and is hence publicly accessible property, despite what the owners of the land on the island may wish to claim. The same applies to freedom to roam in Nordic countries: only the yard of a house and the immediate vicinity is legally protected against trespassing, and the water bodies around the island are freely navigable. There are many thousands of uninhabited islands in the world with potential for commercial development of tourist resorts or private recreational use. Some islands can be bought undeveloped, while others already have roads and/or houses. Islands are also available for rent. Many celebrities have their own private islands. Commercial development of uninhabited islands can raise ecological concerns, as many have a fragile environment. Cruise lines Since 1992 a number of cruise lines have acquired "private islands" to offer their customers exclusive beach experiences. Such islands (or sections thereof) were further developed to have restaurants and perhaps additional attractions such as parasailing, waterparks, zip lines, horseback riding, spas and more. Some islands have piers, others are reached by tender. The purchase of an island allows the cruise line to achieve greater control over the venue and to influence the quality of experience of their passengers. Certain private islands may be used not only by the cruise