San Marino is a microstate completely surrounded by Italy, located on the northeastern side of the Apennine Mountains. It claims to be the world's oldest republic, founded in 301 AD by a Christian stonemason named Marinus. The country's capital is the City of San Marino, which is famous for its three medieval fortresses perched on the peaks of Mount Titano. Despite being an enclave, San Marino is not part of the European Union, though it uses the Euro as its currency and has an open border with Italy. It is one of the world's smallest countries, with an area of about 61 square kilometers and a population of roughly 34,000. Its economy is largely based on tourism, banking, and the sale of collectible postage stamps and coins. San Marino is also known for its unique political system, where two 'Captain Regents' are elected every six months to serve as heads of state.