Pennywise's Lair is the dwelling place of Pennywise the Dancing Clown and is located deep in the sewers of Derry, Maine. In all of its depictions, the lair is a subterranean cavern littered with the bones of IT's victims. It is accessed by a small door, marked in the book and movie duology by a strange symbol.
Miniseries[]
In IT (1990 miniseries), the lair is depicted as a large cave with otherworldly lighting, at least two branching tunnels and a spider web high in the ceiling filled with the remains of IT's victims, including Audra Phillips (who was not dead, only hypnotized by the Deadlights). After IT's death at the hands of the Losers Club, the spider web collapsed and IT's victims descended to the floor of the cave.
Movie duology[]
In IT: Chapter Two, the lair is accessed by climbing down a rocky chasm underneath the floor of Pennywise's circus wagon. At the bottom is a narrow crawlspace, beyond which is the lair. An impact crater where IT landed millions of years ago is the centerpiece of the cavern, and it is here that the Losers attempt the Ritual of Chüd to trap IT in a leather jar. The ritual fails, and Pennywise confronts the Losers in the form of a giant spider/clown hybrid. The cavern also contains many small tunnels and at least one pool of water, all of which lead to personal challenges the Losers must confront. After Pennywise's demise, the impact crater crumbles in a whirlwind as the lair, cistern, and Well House above it implode.