citadel

A citadel is a strong and often high-up building that's usually part of a city or town's defenses. It can also refer to a small area within a city that's very secure.

When people talk about a citadel, they're often referring to an old fortress or castle that was built to protect a city from invaders. These places were usually high up on a hill or a rocky outcrop, making them hard to reach and even harder to breach. Many ancient cities had a citadel in the center, with streets and buildings spreading out from it like a fan. Think of all the famous fortresses you've seen in movies or history books - they're probably inspired by real-life citadels! If someone mentions a "historical citadel" or an "ancient fortress", they're usually talking about one of these impressive structures that helped keep people safe for centuries.