which film ends with people holding hands in a line around the earth?

Hi, I'm trying to find a film and can only remember a handful of scenes.

What I remember...

 - there's some kind of beach fairground attraction with a big door that leads to an underground tunnel where people live
 - someone (some guys kid brother I think) goes in and gets lost.
 - the guy goes in the tunnel and finds loads of people living down there going a bit mad. Looks like a long pale corridor with rooms either side.
 - theme is something about the apocalypse 
 - the movie ends with all these people coming up to the surface and linking hands to form a continuous circle of people around the earth.
 - think it was 90s or early 2000s