Create a spiral staircase in your map

Thanks to gynec for the work put into this tutorial.

1. Change to Grid16 (Grid->Grid16) or press 5.
Press Q and create a brush with the size x:64 y:64 z:256
and a second one with x:160 y:160 z:256
Make the first Brush a Curve->Cylinder
and the second Brush a Curve->Bevel plus Curve->Matrix->Invert.
Now create a third Brush with x:160 y:160 z:16
Must look like this..

 2. Now copy the third Brush 10 times and put on top of each other.
Change to Grid32. Select the Brush below and use the Clipper tool
(or Control+right click, set two dots and press Enter).
Like this..

 3. Thats your first step. Do the same with the other Brushes until you get a 90° bend.