Most have great potential, except the movie type thing. I'm kinda sick of those. If you expand the ramp that doesn't quite end well, it could make for a VERY interesting entrance to secret areas, but it doesn't even have to be all walkable. Make it even more secretive...
The hole isn't quite well flowing enough, the point where the main holes connect need a little better blending, I've done some hole research and made some itneresting ones. See if you can find the blends

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