Location from Avatar: The Last Airbender by Michael Dante DiMartino & Bryan Konietzko
A secret underground facility beneath Ba Sing Se where the Dai Li use hypnosis and brainwashing to erase inconvenient memories — the dark heart of the city's enforced ignorance.
Lake Laogai is where Ba Sing Se's lies are manufactured. Beneath the placid lake surface lies the Dai Li's most terrible tool: a brainwashing facility where citizens who mention the war, question the government, or inconvenience Long Feng are taken and remade. Subjects sit in dark chambers while a spinning lantern casts green-tinged light and a Dai Li agent repeats the trigger phrase until the mind breaks and rebuilds. Jet was brainwashed here. Joo Dee — every Joo Dee — was created here. The tunnels are vast and cold, smelling of damp stone and something chemical. The facility represents the ultimate corruption of earthbending: instead of shaping stone, they shape minds. When Team Avatar discovers it, the true horror of Ba Sing Se's peace becomes undeniable.
The surface appears as an ordinary lake outside Ba Sing Se's walls. Beneath it, a labyrinth of green-lit stone tunnels and chambers stretches underground. Dim lanterns cast sickly light on rows of stone chairs where subjects sit with glazed eyes. A revolving lamp projects hypnotic patterns on the walls. Dai Li agents glide silently through corridors on earthbent paths.
Also known as: Lake Laogai facility, Dai Li headquarters