Should you find yourself on ROCKtropia close to the RRC Subway Race Circuit TP (coordinates 135640, 87964), you might see a message flash by stating: "What the hell was that noise?". Don't be alarmed. It's the Zombie Wave Event area. Basically, within a short radius of the TP, zombies will spawn in waves. Once you kill all zombies in a particular wave, the next wave will commence a few seconds later, bringing more zombies than the last. It's been a while since I completed the wave event, but if my memory serves me well, the last wave is 12. Unfortunately finalizing the wave event does not yield any additional achievements or prizes, though that might of course change in the future. Here's a few additional remarks. In case you think you killed all the zombies but you do not see the message indicating a new wave will start, chances are that they are stuck behind one of the walls surrounding the TP area, or perhaps even within the booth on the corner (I had that happen). Also, the zombies DO count towards the Zombie Prospector Achievements, but NOT towards the BAMF Zombie missions.
