A white hole is the theoretical "other end" of a black hole- things that go into a black hole come out this way. However, the gravitational effects at the singularity in the center of the hole are otherwise the same (and anyone making the trip would be crushed without some form of protection). It would be almost indistinguishable from a black hole.
DC (Pre-Crisis Earth-1), Doctor Who (Expanded Universe)
Some white holes actually draw matter to the "normal" universe from other realities, rather than merely serving as the other end of a black hole in the same universe.