How can I do dark zones

I have a world with dynamic light with his Skylight and lightSource. In this world there is a cave in which I would want to be a dark zone. I tryed to put a PostProcesVolume and tint the zone in black, but the problem is that when i’m far the cave has the normal illumination ans when I approach it all the world becomes dark.
Is there any way that the cave always be dark independently of the position of the player, and not affect the rest of the world?

I put an image in order to you can imagine better my situation.

maybe you could add a second darker skylight, set it to a different lighting channel and have the cave objects only match that new lighting channel. The cave objects will need to be set to ‘movable’ for this to work I think.

But, as I know, I can change the channel light of a skylight.

In case i can change the channel, the cave is a part of a giant static mesh (an island). If i change the channel of all the static mesh, all the island would be affected by this second skylight.

In that case I don’t have a clever solution. I suppose separating the cave parts from the big mesh would give you more flexibility. Or you could assign darker materials to that part of the mesh? Or enclose it with another shape (sphere maybe) which is semi translucent and partially shadows the cave?