You can park at N50°27.700 / E004°52.118
For an organised assault on the citadel you can get a folder at the Tourist office on the car park or have a look at the start point (N50°27.674 / E004°52.031) of the marked routes. Two routes are passing on the cache point and two are passing some hundred meters from it.
It's a small circular box (10 x 10 cm).
Why "the fragrance cache"?
As you will learn about the citadel, Guy Delforge creates his parfums in the Old Artillery laboratory (Also called Colombier Militaire and former Officer's Mess). You can visit his atelier every Saturday's at 15.30 Hr.
The cache is filled with parfum samples. Just exchange them with other one's.