In the fourth volume of Stonehearted, For a Heart Made of Stone, the action shifts to the chateau of Saint-Pol. The Count of Saint-Pol is one of the villains of the story and is holding a tournament, which provides the backdrop for the action.
When I looked into Saint-Pol, I found that it was difficult to get much detail about the castle (it’s now just a ruin) but eventually I came across some good websites that gave me enough to form an impression of the place – and gave me some ideas that contributed to the narrative.
An article on the Flags of the World website about Saint-Pol is perhaps the best historical description of the town and castle. If you read you will see that the castle is divided into an old and new castle – and its the old castle bailey that I use in For a Heart Made of Stone to locate the tournament put on by the Count. The new castle is the location for much of the action. In particular the Wiki Pas-de-Calais site describes the layout in detail (in French – but you can translate using Google!). In particular notice the large round tower used as dungeons – they play a prominent part in the book! Below you can see a great plan of the castle and also an artist’s impression of the new castle. Only a few ruins remain now.