Gollum’s island also known as Slimy island was the home of Gollum during the time he dwelt Gollum's cave in a cave near Goblin-town under the Misty Mountains. The island was made of rock and lay in the center of an underground lake. According to The Atlas of Middle-earth, it was between 150-200 feet from the lake's western shore, near the entrance to the tunnel. From here Gollum had good visibility and could see to the other side and could quickly paddle to and from the island in his little raft.