Intrepid witchers of the world may already have discovered this, as although venturing to the very edge of any World Map results in an invisible wall and a comment from Geralt telling you there's nowhere else to go, if you wait around you'll be presented with a Fast Travel option anyway. Usually the only way to traverse huge distances is to track down the more standard green markers to warp between, but this is a solid alternative - especially if a random expedition has landed Geralt far away from civilisation. Now all we need is a way to trigger this from anywhere within the larger cities, and it'll be perfect.