The phrase "city walls" refers to the protective barriers or structures built around a city in the past. They were built to defend the city from enemies and provided safety to the people living inside. Full definition
It is also the only standing part of old city wall. (traveltoblank.com)
Whatever your tastes, this resort has it all, from the historic city walls, to a bustling art and culture scene. (loveholidays.com)
The place started off like many others as a market town, a hub of agriculture and industry that slowly grew to out live its original city walls. (hookupcloud.com)