This was done using vanilla Blender (vers 2.77a).
(Blend file below)
Hint - save EVERY stage of your work as a separate file until it's done.
Add a tower. (vertical cylinder)
Make a spiral curve. This will be the outer edge of the ramp so it's circumference has to be larger than the tower's.
Duplicate the curve and store it in layer 10 (?) for safety.
Add a curve -> circle and scale it to be the same diameter as the spiral.
Add a vertical cylinder (6 sides) and scale it down to the diameter needed for the vertical railing poles.
Scale it up high enough to span the tower's height, plus a few feet.
Array the pole around the curve so it also fills it.
Duplicate the spiral curve and bevel it with a curve->rectangle. (A plane without a face and converted to a curve with ALT-C will do the same thing)
You should see square ducting spiraling around the tower with the arrayed poles protruding up through the ducting.
Use the Boolean modifier on the poles, naming the 'ducting' as the object. Experiment with all 3 options to see which cuts the poles so they form a spiraled guard-railing around the tower, albeit as yet, disconnected. ("union" did it for me)
Duplicate the spiral curve again and bevel it with a circle this time. (6 sides) This will make the horizontal cylindrical railing for the top and bottom of the poles. Convert that to mesh and duplicate it, raise or lower the copy to sit at the other end of the poles.
The ramp -
Duplicate the spiral again and convert that to mesh (ALT-C).
In Edit mode select all vertices and extrude (E), scale the new vertices inward so they penetrate the tower.
Note - Disable the scaling Z axis with SH-Z so the ramp remains horizontal when scaled inward.
Adjust the ramp's height to match the bottom of the poles and lower railing.
When all is scaled and positioned correctly, the result should be as in the 1st pic above.
It would probably pay to parent all components to the tower, and after, disable their selection in the Outliner, so they don't get inadvertently selected. Move the tower to drag it about as a single model.