In Toledo's two thousand year history, it's been tossed around among invaders like a frisbee, so it's no surprise that it's encircled by a formidable defensive wall. It served as the capital of Visigoth Spain, and remained an important city when it was captured by the Moors in 712. When it was reconquered by Castile in 1085, it served as a frontier city from which further Christian incursions into Moorish territory were launched. The present set of walls dates from that period, when the Christians assumed Toledo would be won and lost many times in the war against the Moors. They overestimated the Moors' tenacity, who, after a thousand years of war were more into debauchery than reconquering lost territory. So the walls were able to stay pretty much as built, and are a great addition to the city's beauty.