It’s set in a nice park area and you can walk around the citadel fortifications anytime for free. The main building you can’t really go in as the army/ministry of defence use it which is a disappointment. It’s hard to get a good view of it.

What better way to rest from the hustle and bustle of the city, and to digest after a good meal in an estaminet, than to take a good digestive walk in this large Lille park that has kept a natural, almost "wild" side. The change of scenery is total and will allow you to recover from the noises of the city. I particularly recommend the walk that goes all around the Citadel.

A very pleasant place to walk around the citadel. The interior is occupied by the European armed forces. This citadel is the first site of the illustrious Vauban (more than 100 projects in France) and he applied his defensive principles there. The walking path is a round between ramparts that could be flooded to repel the attackers. The central structure is a pentagram surrounded by a nested succession of triangles (an aerial view is available on the web). Behind the walls, mounds of earth on which trees were deliberately planted from the outset as protection. Over time the citadel has become a green lung of Lille. A beautiful walk with the esplanade nearby

On the edge of the city, in a shady and quiet space, nice place to take a little walk or bike ride. We can't go inside, it's still a military place. The tour of the fortified enclosure allows to see the marshes, the pastures for horses, pony and cows, to get "lost" in the deadlocked paths (many overlook fenced places). As already written, there is also a small Attraction Park and nautical rentals nearby.

The Citadel is an amazing architectural jewel. The history of the site is very interesting. It is a functioning military base, however you can gain access through an organised tour. This is very highly recommended. Otherwise, you can get as far as the 'drawbridge'.