Undermountain

Undermountain is a vast labyrinth of caverns under the area of Waterdeep in the fictional world of Forgotten Realms. It is at least nine levels deep and possibly more. These caverns' true creators are unknown. Currently Halaster Blackcloak is rumored to use Undermountain as his playground (307 DR - 1370 DR). The lower 3 levels were delved by dwarves. Below that not much is known of Undermountain. The upper levels house many famous sites such as Skullport, also known as the Port of Shadows. Qilué and the Promenade of Eilistraee, a temple complex North-east of Skullport dedicated to the good aligned followers of Eilistraee. Both of which are on the third level.

Madgoth's Castle also lies below the depths of Undermountain.

Many gates lead into Undermountain from all over Faerûn.