sewer space

   0   1   2   3   4   5 

4          +---+---+      4
           |       |    
           |       |    
3      +---+   +   o---o---cit
       |           |    
       |           |    
2  +---+   o---o   o---o  2
   |       |   |       |
   |  urb  |   |       |
1  +---o---o   o---o---o  1
       |   |
       |   |    
0      +---+---*          0

   0   1   2   3   4   5 

cit = back entrance to citadel
urb = stairs to urban area
o = landmarks (first aid packages)
* = store room (dead end)