The Isle of Drear is a small island located off the northernmost tip of Scotland. The Isle is the home of the Quintaped, and has been made Unplottable for this reason.
Behind the scenes
The map feature that replaced the Gateway on Pottermore on 31 July, 2013, features a small island off the coast of Britain, with a Quintaped marked on it — making it the Isle of Drear. While this may challenge the notion that the Isle is Unplottable, it should be noted that Hogwarts Castle, another location known to be Unplottable, is also featured on the map.