This UNESCO cover from Slovakia depicts a set of 2 stamps issued in 2009, celebrating the
Danube Roman Limes. The Danubian Limes, a network of fortifications along the Danube river, protected the borders of the Roman Empire. The site is shared with Germany and Austria. Six sites at two locations, of military camps Celemantia and Gerulata, are listed in Slovakia. In 2021, the western segment of the Danube Limes were inscribed on the UNESCO World Heritage List as part of the set of "Frontiers of the Roman Empire" World Heritage Sites.
