The headquarters appear to be situated inside an under contruction complex of at least four towers, left unfinished by the outbreak, with the most prominent tower situated to the southwest end of the complex. It is neither known what purpose the complex's towers were meant to serve, nor who ordered their construction, or even when the project started, though it is obvious that this was a very large-scale project, given the height of the southwest tower. There also appears to be a fifth and sixth tower under construction, though they are both still at the foundation digging stage.
As mentioned earlier, Rais and his organization have at some point taken over the unfinished complex and use it as their headquarters, with one of the two foundation holes for the implied fifth and sixth towers used as Rais's personal arena, where he makes people fight to death against captured zombies stored in containers, with one of these people being Crane. It isn't known what Rais and his men used the rest of the complex for, since only the arena is seen during the first visit, and when it is visited for the second time, it's been overun by zombies, and all of its non-zombies occupants have been killed by Rais himself.