I was doing the exercise (https://kwiziq.learnfrenchwithalexa.com/my-languages/french/exercises/judge/1833/14548249?response=4150265&page=7) to answer a question and now have one of my own:
There's the phrase: visiter les ruines du vieux château.
How come the rule that the definite article is omitted if there's an adjective intervening between de and the noun is not applicable here? I would have thought this should be ...de vieux château.