Block 441 is a high-security storage facility located several hundred meters underneath the main metropolis level, and was previously owned by Rhombus Corporation before it was dissolved. The five hundred storage facilities that is owned had since then been abandoned. The facility was flooded with stagnant water a few months after it's abandonment, driving out the flocks of homeless people and making it uninhabitable.
Ghost_K Team had found the place almost five years ago, and using their elemental skill drained and rebuilt the place to make it habitable, transforming the gigantuan block 441 into their headquaters. Since then they have also moved into blocks 440 and 439 nearby to make room for storage and other facilities, however the rest of the facility is remains empty.
The ossacional Chute Scavenger pack does manage to find their way all the way down here, but they are usually disposed of by Ghost_K's security drones.