Does India count? China? Russia? Spain? France?
India has tons of mutually unintelligible languages. China does too (some call them dialects). Spain has multiple partially mutually intelligible languages -- and Basque is an isolate (and mutually unintelligible). IIRC Occitan and French are not that compatible either.
Maybe you're thinking about the Basque language instead? I'm from the south of France, Occitanie really. Occitan is certainly different from French, but not completely alien. It's a bit similar to Spanish in closeness. Basque on the other hand is very different and is an isolated language.
No, I know that Occitan and French are not that different, but they're still pretty different. Like you say, similar to Spanish in closeness -- I would definitely consider them distinct languages that take effort to learn.