Hidden Hollows are a new feature for Pokemon Black 2. These Hollows are located between a gap between two trees. There are Fifteen Total Hollows within the game.
These Hollows can have items, Pokemon with their Dream World Ability, or items that can be found with the Dowsing Machine within them.
These Hollows can be found on Routes 2, 3, 5, 6, 7, 9, 13, 18, 22, and 23. They can also be found in Lostlorn Forest, the Abundant Shrine, Sangi Ranch, the Giant Chasm, and Pinwheel Forest.
After you have obtained the Pokemon or items within the Hollow, more items and Pokemon may return to the Hollow. The more steps you take after obtaining the Pokemon or item, the higher the chance of another item or Pokemon being in the Hollow.
Added by: Warrior13 Aug 8th 2012, ID#17286