After Carcassonne in southwest France, Visby lays claim to the most important and best-preserved medieval city walls in all of Europe. The town’s citizens began building the original six-meter-high (20-foot) fortified walls in the 13th century, and they eventually grew to over 11 meters (36 feet). Today, the wall still stretches for 3.4 kilometers (2.1 miles). Walk in its shadow and explore the 36 intact medieval towers as well as numerous gateways. The North Gate offers the most impressive view of the wall, providing a sense of its enormous scale. St. Mary’s Cathedral, a few blocks inland, also dates to the 13th century.