Examples:
setcell "arena",0,0,300,300,cell_basilica,1;
setcell "arena",140,140,160,160,cell_basilica,0;
setcell "arena",135,135,165,165,cell_walkable,0;
setcell "arena",140,140,160,160,cell_walkable,1;
From const.txt:
cell_walkable 0
cell_shootable 1
cell_water 2
cell_npc 3
cell_basilica 4
cell_landprotector 5
cell_novending 6
cell_nochat 7