Planning and greyboxing

Taking some of these points into account, i set about drawing up some floorplans for my map.

Bottom floor (Top Left) Middle Floor (Bottom Left) Top Floor (Right)

I tried to structure the area so that player always has a route to the atrium. I wanted to include a corridor system that looped all the way around the atrium and provided access to balconys which overlooked the area. With so many vantage points it makes the centre of this room a good place to place a powerful pickup/weapon as it is a high risk route to take. Each room has at least two exit points meaning players are never 'trapped' in a room without a safe route out.