The Ancient Cavern is an area reached from the whirlpool near Otto Godblessed's house, which was released on 3 July 2007. A player must dive into the whirlpool to enter the cavern, which contains many high-level monsters, including a high level metal dragon, the mithril dragon.
Fighting these dragons is one of the two possible methods of obtaining a dragon full helm without having to purchase it from another player. The dragons occasionally drop the helm directly. They also occasionally drop chewed bones. Lighting a pyre ship made with chewed bones releases the spirit of a departed barbarian, who occasionally rewards the player with this rare piece of armour.
The cavern is in a members-only area and can only be accessed after the player has completed the first Firemaking activity in Barbarian Training, which requires level 35 Firemaking. After that, the player must ask about making pyre ships, and then will be granted access to the dungeon in order to fulfill the objectives required to make them. (Barbarian training is also required to be able to make pyre ships.) If a player dives into the whirlpool before completing these tasks, they will be swept away, losing a small amount of their life points, eventually washing up on the shore near Hadley's house.
Players cannot leave the cavern via the whirlpool. Instead, they may leave by riding on one of two aged logs that can be found near the waterfiends. The logs are floating on the water, as shown on the map, and have examine text of "A log jammed by the current, perhaps rideable."
A fairy ring, also located near the waterfiends at the western end of the lower level, can be restored for use by players who can use the rings. With a spade (toolbelt works) and 5 bittercap mushrooms in their inventory, the player can restore the ring by planting the mushrooms on the "Enchanted land" spot near the centre of the ring. After it is restored, players can use it to quickly teleport in and out of the cave. The fairy ring code is B•J•Q.
A follower can't be taken into Ancient Cavern by the whirlpool, but instead, one can use the fairy ring to do so. This is especially useful for bringing a clan avatar for the 6% experience boost.
A player diving into the whirlpool.
The Ancient Cavern is one of the more dangerous dungeons in RuneScape. All who enter the area should be prepared to face dragons with long-range attacks, and high-level monsters that can attack using more than one combat style. None of the monsters in the Ancient Cavern, except skeleton heavy, can be poisoned.