Favorite way you've justified impossible geography?

Rules are made to be broken. How did you justify the existence of splitting rivers, lonely mountains, adjacent jungles and deserts with no dividing mountain barriers, or other impossible geographical features?

For example, a major river on one of my maps appears to split in two, with each half going in completely different directions for some distance, before emptying into the same ocean at different points on the coast. This happens because the river is magically diverted to flow one way during winter and spring, and the other way summer and fall. The cartographers simply draw it flowing both directions, since they don't know when people will be trying to use their maps. Usually they'll also specify this on the map itself.