The first place I hit up was Wikipedia and their article on the Castle. It has a fascinating history, covering several centuries. At one point, the site was visited by Joan of Arc! It also served many masters, including the infamous Cardinal Richeleiu, the villain in the Three Musketeers.
After reading about the facility, I found out that Jacques was held in a prison tower known as the Tour du Courdray. I went on a search to find pictures of this castle, only to find a great video tour of the Tour du Courdray. While the video is in French, it's still worth while to watch, as it gives you a better idea of the layout of the castle.
The next time you and your Chapter perform a DeMolay Degree, you can think back to where Jacques was held for some inspiration!
Frat! ~ "Dad" Seth Anthony