Nest of Maggots

The Maggot's Nest is a place in Seireitei which serves as a prison under the supervision of the Onmitsukudō's third division. On the inside, it resembles a cave with an area for prisoners.

When a shinigami becomes a potential danger to other shinigami and Soul Society itself, then that shinigami is brought to the Maggot's Nest for imprisonment, even if that shinigami wasn't proven guilty in any way. This was to ensure that no danger will be brought to Soul Society. No prisoner is held inside a cell (since they can't set foot outside the prison either way) with the exception of Mayuri Kurotsuchi (about a century ago) which implies that he is of high-level danger.

Kisuke Urahara was once in-charge of the Maggot's Nest before being promoted to Captain of the 12th Division.