I seem to recall some film that is probably from the era of "20 000 leagues under the sea". Maybe it's a sequel, I don't know. For some reason I thought it was called "For whom the bell tolls" or similar, I think I remember the line used in the film.

All I can remember of the premise is that there's maybe an underwater city, it's accessed via some tunnels or something. Might be atlantis. Some explorers end up there and are pseudo-prisoners like in 20 000 leagues. Some "story" about bells ringing signalling a death or tragedy/prophecy. I think near the end there's a volcano or something and it causes the bells to ring as the city sinks/floods, but the heroes escape?

I remember that film too, I wonder if it is that one, or another one altogether. Guess I'll have to track it down and watch it