download the voxlap cave demo and take a look at it.
It might not look like much at first, but after looking around a map for a while, try this.
Pick a large object of some kind, line yourself up with it, and just keep shooting.
watch as your shots dig a hole in the object, then as they bounce around, start carving out a larger area inside of it.
go inside the tunnel your shots made, and carve out branching tunnels.
Find the super blaster and blow up half of a mountain.
If this is the future of fully destructible environments in games, I can't wait...