Greece is located in the European continent and its oldest nations, and covers an area of 131,940 square kilometer. It shares its borders with countries including, Bulgaria, Macedonia, Albania and Turkey. Athens is the capital city of Greece and a home to almost one-third of the Greek population. Athens is famous for its ancient buildings, such as the 2,400-year-old ruins of the Parthenon temple, and the Acropolis. The Greek people have a strong national unity, based on their deep-rooted Orthodox religion, and a language that has remained use for 2,700 years. Three-fifths of the Greek is mountainous, and only one-third of the land is cultivated. The poor soil is difficult in Greece. Agriculture employs about twenty-three per cent of the work forces mainly on the traditional farms. The main crops are citrus fruits, grapes, and olives. Greece is the world's third largest producer of olive oil. Tourism is the mainstay of the economy and employs thousands of Greeks each summer.