I won't consider it keyword stuffing for one reason:
According to Google Irrelevant keywords:
"Keyword stuffing" refers to the practice of loading a webpage with
keywords or numbers in an attempt to manipulate a site's ranking in
Google search results. Often these keywords appear in a list or group,
or out of context (not as natural prose).
The most important fact here is that your URL is representing the content of your page.
So as for an User Experience point of view, which is one of the most important topics in SE like Google, I wouldn't be surprised if the name of that castle also has the name of the castle in their original name.
If this is a good slug scheme or the content of the slug can be different is another story, but doesn't seems to be keyword stuffing at all.