The fortified city of Carcassonne is Europe's largest preserved medieval town, surrounded by 3 kilometers of double walls and 52 towers. Controversially restored in the 19th century by Viollet-le-Duc, it is now a UNESCO World Heritage Site. Access to the old town is free 24/7 — you can wander its cobblestone streets anytime. Only the castle and ramparts require a ticket. The city comes alive at night with atmospheric lighting.