Spellhold

Spellhold is an insane asylum located on the island of Brynnlaw, one of the Nelanther isles, off the western coast of Amn, under the command of the Cowled Wizards of Amn. They use the asylum to house the 'deviants' they have found in Amn, practicing magic without an official license. There is a portal to the Underdark in a secret room on the main floor of the building. The building itself is connected to a magical dungeon, which was rarely used to test inmates to see if they are sane enough to leave.

Appearances
The cursed elven mage Jon Irenicus was sentenced to Spellhold for casting illegal arcane magic within the confines of Athkatla. While being imprisoned, he was too powerful to contain and killed all of the Cowled Wizards who resided there, taking over the facility to perform his own experiments. Irenicus' vampire sister, Bodhi used the dungeon as a hunting ground to toy with those who made it there.
 * Baldur's Gate II: Shadows of Amn