From the lowest dungeon to the highest peak it climbed, ascending in unbroken spiral in many thousand steps, until it issued at last in Durin’s Tower carved in the living rock of Zirakzigil, the pinnacle of the Silvertine. There upon Celebdil was a lonely window in the snow, and before it lay a narrow space, a dizzy eyrie above the mists of the world. The sun shone fiercely there, but all below was wrapped in cloud.
- The Two Towers (Book 3), Chapter 5
Celebdil (or Silvertine) is one of the three Misty Mountains under which the Dwarven realm of Moria lies. On its peak sits Durin's Tower, the high end of the Endless Stair. Erected in ancient times, the tower has been lost for millennia and is now considered only a legend among the Dwarves.