What do we call the large protective walls around a medieval town?

The story behind the answer

Medieval towns were encircled by massive stone ramparts with towers, battlements, and fortified gates to resist siege and control entry. Watchwalks let defenders patrol, and gatehouses and barbicans funneled traffic for inspection and taxation. Unlike a keep (the stronghold inside a castle), a moat (a surrounding ditch, often water-filled), or a palisade (a wooden fence used for lighter or temporary defense), these continuous masonry fortifications defined the town’s outer boundary.

Beyond protection, they signaled a town’s privileges and autonomy: gates closed at night, tolls were levied by day, and markets flourished safely within. In the gunpowder era, many were reshaped into star forts or dismantled; some became grand boulevards (like Vienna’s Ringstraße), while others, such as Carcassonne, remain striking examples of medieval urban defenses.