It is an abandoned building standing in the bosom of the mountains. There are stagnant violent puddles resembling blood that covers the floor and out front are a bunch of spider lilies, with the shade of crimson.
The walls are rotten and the old wires dangle from the ceiling. The window frames are missing, most of the equipment is stolen and the hospital rooms are just home for insects. 
Kunikida and Dazai went to the abandoned hospital to investigate about the terrorist incident. While exploring the place, they found a black cord that seems to be a new one and follows its direction to which they find someone screaming for help and that person is Nobuko Sasaki trapped inside a water tank.
This is also the place where Nobuko Sasaki reveals herself as the Azure Messenger.