Of Earth's 196 independent countries, San Marino is the fifth smallest and – arguably – the most curious. How it exists at all is something of an enigma. A sole survivor of Italy's once powerful city-state network, this landlocked micronation clung on long after the more powerful kingdoms of Genoa and Venice folded. And still it endures, secure in its status as the world's oldest surviving sovereign state and its oldest republic (since AD 301). San Marino also enjoys one of the planet's highest GDP per capita, but some say it retains a curious absence of heart and soul.