San Marino, officially the Republic of San Marino ( san-mə-ree-noh; Italian: Repubblica di San Marino, also known as the Most Serene Republic of San Marino), is a country situated on the eastern side of the Apennine Mountains. It is an enclave surrounded by Italy. Its size is just over 61 km (24 sq mi) with an estimated population of over 30,000. Its capital is the City of San Marino. One of the European microstates, along with Liechtenstein, the Vatican, Monaco, Andorra and Malta, San Marino has the smallest population of all the members of the Council of Europe. San Marino is the oldest surviving sovereign state and constitutional republic in the world, as the continuation of the monastic community founded on 3 September 301, by stonecutter Marinus of Arbe. Legend has it that Marinus left Rab, then the Roman colony of Arba, in 257 when the future emperor, Diocletian, issued a decree calling for the reconstruction of the city walls of Rimini, which had been destroyed by Liburnian pirates. The constitution of San Marino, enacted in 1600, is the world's oldest constitution still in effect. The country's economy mainly relies on tourism, and San Marino's culture remains Italian, mainly Emilia-Romagnan in essence. It is one of the wealthiest countries in the world in terms of GDP (per capita), with a figure comparable to some of the more developed Italian regions, such as Lombardy and South Tyrol. San Marino is considered to have a highly stable economy, with the lowest unemployment rate in Europe, no national debt and a budget surplus.