From the World Heritage inscription:
San Marino Historic Center and Mount Titano covers 55 ha, including Mount Titano and the historic center of the city which dates back to the foundation of the republic as a city-state in the 13th century. San Marino is inscribed as a testimony to the continuity of a free republic since the Middle Ages. The inscribed city center includes fortification towers, walls, gates and bastions, as well as a neo-classical basilica of the 19th century, 14th and 16th century convents, and the Palazzo Publico of the 19th century, as well as the 18th century Titano Theater. The property represents an historical center still inhabited and preserving all its institutional functions. Thanks to its position on top of Mount Titano, it was not affected by the urban transformations that have occurred from the advent of the industrial era to today.
San Marino is one of the smallest countries on Earth. It is a legacy of the time when the Italian peninsula was made up of city states. It is the world’s oldest republic and also was the home of the only elected communist government in the world at one point. The entire economy of the country seems to come from tourism now. Every business on Mount Titano (which is most of the country) seems to be orientated towards tourism. The coat of arms of San Marino has three towers on it which represent the three towers which dominate Mount Titano.
View the complete list of World Heritage Sites I’ve visited.