From MineScape Wiki
Crandor is a small volcanic island north of Karamja, Players can access Crandor during and after the quest Dragon Slayer. During the quest you have to enter the mountain with a ladder at its very peak at the end of the pathway. The entrance to elvarg's cave. Only one person may do that part of the quest at a time. Currently the dragon is bugged and if you press the button but do not enter or you die without finishing the quest you cannot re enter the chamber.
Location is currently unavailable, and information incorrect.