2d map elevations

2d map elevations

I was wondering if anyone had any samples of how elevations are done on a 2d isometric map. At first I thought it was sort of like a illusion but I have seen some systems on youtube where you seem to fall off of elevations. Even elevations that are trasparent underneith so the tiles look like they are floating.

Maybe I dont understand 2d maps enough Im not sure. A 2d isometric map with elevations seems difficult to me to figure out.