I had a great time building this and I am sure you will to.
Step 1: Inside Area
Make a 70x41x10 block room. (you do not need to add the pillars)
Step 2: Outside Area
Add a 41x8x8 hall along the front with a 8x10 block extension. Then add a 70x20x8 area along either side with a 10x10 area in the front corners.
Step 3: Walls and Ceilings
Add ceilings and walls.
Step 4: Towers
Add 10x10x6 towers (as many as you like.) Then Add two 7x7x6 towers in the corners of the extension.
Step 5: Floors and Furnishings
Add floors and furnishings. This is some of what I did.