Access the right half via The Hall of Crafting or Ring of Law.
Access the left half via The Grim Guzzler or The Chamber of Enchantment.
The Heart of the Mountain, Location 6.
This area overlooks The Black Anvil and is divided into two parts.
The left half provides access to The Vault, where the quest The Heart of the Mountain can be completed.
The right half provides access to The Chamber of Enchantment, which leads further down the dungeon.