The Angel's Hole is the training ground of the Mazinger Angels. It is a hidden facility that is only known by higher ups in their organization and any recruits or guests have to be blindfolded to keep the area a secret.
The Angel's Hole purpose as a training facility includes a dojo where trainees go for combat utilizing a training armor and rods. A special training room to control robots through movement is also featured, but only for certain kinds of robots like Minerva X. There are also living quarters, a shower room, and docking bay for the Angels' robots'.