It's a default map in the game. It's also where all the portal to your custom maps will be.
To get to it from Bonfire Island (default place a new character will appear, also first map you enter) go through the tunnel (Ficho Tunnel) and follow it all the way to the end. Go through that portal and you will get to Flourite Plains. If you zoom out in the little map (upper left corner) you'll see a little 'island' south east of the mainland. Go there and you'll find the portal to Cape of Distant Worlds.
