Privacy, your very own mining field with very large roids. That translates to lots of isk.
Hidden belts do not show on the main screen when you right click for locations. What happens is you warp to some location and way, way off in the distance you see a glimering of a roid and start thrusting to that flicker, it may be 200-300k away from your "known" warp point. Once there you discover it is indeed a ore field and after you right click on screen you realize it does not show up! Make that bookmark, get your secure cans and you mining ship and get busy! No one can warp on top of you and rats will likely be minimal.

Hidden belts can be part of a known asteroid belt that just simply moves into another grid. Others you need to find on your own using the scanner.For POI just go to system belts and to a max range scan and see what you come up with, if within 5k you can warp to(might take a while) but sometimes well worth it!! You can try checking out the fugitive hideouts I found some omber roids at 0.5-0.8 systems some worth 30 to 40 mil. GOOD LUCK MINERS!