The most accessible walls on our list are in Dubrovnik, Croatia. Located along the Dalmatian Coast, Dubrovnik's first defensive structures were built in the seventh century. Many additions and renovations took place over the next thousand years. The city walls that stand today were constructed during the Middle Ages and define the geography of Dubrovnik, even today. Running uninterrupted for more than 6,000 feet, they reach a height of more than 80 feet, while the distinctive towers are even higher.