Rising into the cavern was an odd sensation, as if the poles had flipped, or if gravity had simply ceased to exist. It was a flipping, churning sensation in Hermione’s stomach that reminded her of falling in a dream. They were underwater,  miles  in fact. But it was almost as if at the bottom of the ocean, once you reached the deepest depths, you would find an alternate dimension, resurfacing in a new world, opposite the one you'd left. 