This popular winter resort is one of the fastest-growing resort cities in the USA. Surrounded by a ring of five mountain ranges in the Sonoran Desert, it is known for its constant sunshine; and its location, only 160km (100 miles) from the Mexican border, is apparent in its architecture, cuisine, lively fiestas and cultural festivals. The Tucson Children’s Museum, with many hands-on exhibitions, is a favorite with children and adults alike, as is the zoo at the Arizona-Sonora Desert Museum. Some 48km (30 miles) north of Tucson, visitors to the State can be dazzled, if not alarmed, by the gargantuan bubble that is Biosphere 2 - a Plexiglas bubble laboratory containing five separate and self-contained ecosystems. It was designed to help scientists colonise Mars but a series of mishaps has plagued this project; even sightseers do not come in their crowds any more (during the early 1990s it was one of the State’s most popular attractions). It is nevertheless worth a look, if only from afar. Guided tours are available.