Location from Worm by Wildbow
An inescapable parahuman prison buried inside a hollowed-out mountain in the Rockies. No guards inside. No release. Inmates self-organize into cell blocks ruled by the most powerful among them.
The Birdcage is the endpoint. Parahumans sent here never leave — there is no parole, no appeal, no escape. Dragon designed and maintains it, monitoring from the outside through automated systems. Inside, the inmates have organized into cell blocks, each controlled by a powerful cape who maintains order through force or influence. Marquis runs one of the most stable blocks. Lung was sent here after his capture. Teacher manipulates from within. The prison is designed so that even if inmates breach their block, they face layers of containment — vacuum seals, containment foam, tinkertech traps — before reaching the surface. The social dynamics inside are complex. Some blocks are civilized. Others are nightmares. Everyone knows they're never getting out, and that knowledge shapes everything.
From outside, a mountain face with a single fortified entrance tube. Inside, a vast hollowed cavern system divided into cell blocks connected by tunnels. Each block is a self-contained community with fabricated living spaces, common areas, and workshops. The architecture is brutalist concrete and reinforced steel. Dragon's containment systems honeycomb the walls. Light is artificial and constant.
Also known as: Birdcage, the Cage