The High Rock sea coast is the region in the upper left corner of the overland map. It is the place where the ships of the player are anchored after being bought. Every time the player enters his ship via the Transportation-Menu, he will be sent to this area. One can actually travel from this location to any other location on the map, both in fast-travel mode and normally. However, it is not possible to travel to this location by any other means than by entering the ship, since the player's position, which is displayed on the overland map, is too inaccurate to be of real use for the orientation.
To the northwest of this area is the entrance to the Mantellan Crux. But since one would normally enter this place via teleportation, this entrance would only be useful under certain conditions (e.g., if one wants to re-enter the Crux after leaving prematurely).