I had 5 layers  representing the roof, platform, stairs, rail, and tower in 5 different colors. The stairs was the hardest part in creating. I utilized the 3D modify.align though out the drawing and I had to rotate 2D around the given UCS pointer. To trim the stairs I used the modify.solids union and subtraction

Creating the ground is accomplished by setting surftab1 and 2 to 100 units and use surface mesh command

using the x-ref command you can bind two AutoCAD files