In Scwarzschild's geometry, wormholes exist at the intersection of black holes and white holes. Two universes connect there. Theoretically, wormholes allow for time and space travel. However, they violate the second law of thermodynamics so our experience of them is limited to software examples.

In FishNtheSea wormholes allow the player to travel through time and space by clicking on certain living organisms that inhabit multiple locations or times.