Creating a garden on a relatively small lot (1600 m2) that slopes at a 45 deg angle is definitely a trick.  But this garden by Secret Gardens of Sydney makes is look easy (kind of).  The carved hillside is beautifully sculptural and interesting without being overwhelmed by the many retaining walls.  I am also interested to study the steps and how they weave among the walls.   What are you learning from pictures of this garden?