The birthday gift that just kept gifting: 1.5 miles of wall, 88 semicircular towers, 9 gates, 10…read morefeet thick and 39 feet tall, basically an Iron Man suit for an entire city. Built starting 1090 and reiterated through the 14th century. Don't forget the Roman foundation stones for additional stability. It's said to be the best preserved medieval city walls in the world. Remarkable!