The Most Serene Republic of San Marino (Italian: serenissima repubblica di san marino) is the third smallest nation in Europe (after Monaco and Vatican City). Located in southern Europe, it is an enclave surrounded by Italy, and is one of the European microstates. According to legend, San Marino is the oldest constitutional republic in the world still in existence today. It was founded in AD 301 by Marinus of Rab, a Christian stonemason fleeing the religious persecution of Roman Emperor Diocletian. San Marino is the fifth least-populous sovereign country in the world (larger only than the Vatican City, Tuvalu, Nauru, and Palau).