Lutherstadt Eisleben is a town in Saxony-Anhalt, Germany. Martin Luther was born in this city in 1483. Martin Luther was a German professor of theology, composer, priest, monk and an important figure in the Protestant Reformation.
Luther rejected several teachings and practices of the Roman Catholic Church. He strongly disputed his understanding of the Catholic view on indulgences, that freedom from God's punishment for sin could be purchased with money. In the end it resulted in his excommunication by the Pope and condemnation as an outlaw by the Emperor.
Luther Memorials in Eisleben and Wittenberg is a UNESCO World Heritage site.
But... as Dustin pointed out in the comments, only the houses in Eisleben where Luther was born (1483) and died (1546) are included in this Unesco site. So in the end this postcard can't be marked as Unesco.