The walls of the old town, Dubrovnik, Croatia

In 1979, UNESCO made Dubrovnik's Old Town a World Heritage Site, including much of the ancient city walls. They surround the city on all four sides and keep a respectable collection of historical monuments, including towers, castles, churches, monasteries, squares and streets, schools, museums and galleries. These stone walls erected for the purpose of defense, to protect its citizens since the founding of Dubrovnik in the VI century.