Slowly inch forward. You will hear your footsteps change from stone to metal. Follow the particle trail for 15 meters until you hit a wall that wasn't there before.
Walk along the perimeter of every map, especially in dark, shadowed areas or behind large buildings. zombie shooter 2 secret locations high quality
The gap is actually an invisible bridge . You need to walk off the edge onto thin air. The fog effects in Zombie Shooter 2 obscure this, but if you look closely (again, high-quality rendering helps here), you can see faint shimmering particles in a straight line. Slowly inch forward