| First thing to do is turn off the "snap
      to grid" from the Map Manager. Then select the grid length
      to World Unit. Now, start drawing lines. Hold down the option
      key to constrain the line length to the current grid setting(in
      this case 1 W.U.). | 
     | 
  
  
      |  
    I. To start making curvy walls, draw
      constrained lines one after the next. Each time, increase the
      angle of the line a teeny bit. To change the radius of the curve
      you're making increase or decrease the angle of the line. | 
      | 
  
  
    | II. Ok, so you're wondering where
      the trick is right? Now draw some guidelines. Take the first
      few points you've placed, and draw lines either horizontally
      or vertically from these. In our example we've used horizontal
      lines, which means that we'll extend the curvy wall around to
      the right. | 
      | 
  
  
    | III. Use the Guidelines to continue
      the curve. Keep drawing constrained lines from the last one you
      added, and simply have the point end on the guideline. This way,
      you can make the curve symetrical. | 
      | 
  
  
    | IV. We've deleted the guidelines from
      our example and started adding lines that will later form the
      facing side of stairs. Again, we're making these lines a constrained
      size, this way we can have the inside of the stairs match the
      outside curve. You have to draw these new lines so they bisect
      the angle between the two lines on the outside of the curve.
      (Note that we did a very poor job of bisecting the lines in our
      example.) | 
      | 
  
  
     
    | V. Now draw the inside of the the
      stairs by connecting each of the lines we just drew. Of course
      here you don't want to constrain the size of the lines, just
      make them as long as they need be to complete each stair. | 
      |