I've done two quests here, wandered all around the little island, come in on all three different bridges but the only thing I discover for this location is a wayshrine. I've seen a map online that shows a fort/castle icon for this place, but there isn't one on my map in game so I'm just wondering if this isn't actually supposed to be discoverable, or if there's some kind of bug going on. Has anyone else actually discovered the tower itself not just the wayshrine?