San Marino is the world's smallest republic, although when Nauru gained independence in 1968 it challenged that claim. Nauru's land mass is only , but its jurisdiction over its surrounding waters covers , an area thousands of times greater than the territory of San Marino. San Marino became a member of the Council of Europe in 1988 and of the United Nations in 1992. It is not a member of the European Union, although it uses the euro as its currency (despite not legally being part of the Eurozone).