Tourism is estimated to contribute up to 24% of Cornwall's gross domestic product. In 2011 tourism brought £1.85 billion into the Cornish economy. Cornwall's unique culture, spectacular landscape and mild climate make it a popular tourist destination, despite being somewhat distant from the United Kingdom's main centres of population. Surrounded on three sides by the English Channel and Celtic Sea, Cornwall has many miles of beaches and cliffs; the South West Coast Path follows a complete circuit of both coasts. Other tourist attractions include moorland, country gardens, museums, historic and prehistoric sites, and wooded valleys. Five million tourists visit Cornwall each year, mostly drawn from within the UK. Visitors to Cornwall are served by the airport at Newquay, whilst private jets, charters and helicopters are also served by Perranporth airfield; nightsleeper and daily rail services run between Cornwall, London and other regions of the UK. Cornwall has a tourism-based seasonal economy.