The Retaining walls are optional components to the design. The stairs are 6" risers, 15" Tread.
The drawings didn't clearly show the practical aspects (i.e. how would planters in steps be maintained). The lawn at 16 feet is a flat lawn, not the sloping one as shown in drawings- i.e. no relationship between planters, staircase and retaining wall shown. But its a usable design, simple and looks good- figured out practical bits ourselves!