20 Euros UNESCO

San Marino's annual gold UNESCO issues are struck under the terms of the monetary agreement between the Republic and the European Union — an arrangement that grants San Marino the right to mint euro-denominated coinage despite not being an EU member state. The 2018 issue falls within a long-running commemorative series, each edition tied to a specific UNESCO World Heritage theme.

Struck at the Istituto Poligrafico e Zecca dello Stato in Rome on San Marino's behalf, mintages for these issues are tightly capped, and the series has historically sold out quickly through official channels.