I visited the Arras Citadel in summer 2010. This Citadel now seems to be also part of a nomination called "Les villes bastionnées des Pays-Bas."

But the gate was locked and tourists were not allowed in. 

All I could do was to take paths around the Citadel that are closest to it, beginning with the road between the citadel and a cemetery just north to it. You can hardly see the inside of the fort but can see the outside from various points along the paths. These paths had been created for hiking and biking. 

If you are disappointed, the cemetery to the north is in fact one of the "Sites funéraires et mémoriels de la Première Guerre mondiale" TWHS, so you can walk in to look around and pay respects to the soldiers who fell at the Western Front during the WWI. 

Arras also has a belfry in the center inscribed on the WH list.

So Arras has 2 sites inscribed and will possibly have 4 sites inscribed in the future, making it perhaps the most decorated city in France. 

Revised: 28/04/2022