Multilevel landscape design includes a combination of retaining walls of varying heights, flat terraces, moderately sloped areas, and landscape features that are created together with walking paths and stairways. For a grand, formal look, route the stairs straight up the middle of a series of retaining walls. Alternatively, break up the landscape by using the stairs to go from one terrace to the next in different areas, using pathways along the terraces to connect them.
Wherever access by foot is not needed, it's fine to leave the slope steeper (no more than 45 degrees) and use those areas just for planting. You can make planting shelves, like mini-terraces, to create a focal point, as well as flat ground to plant on, for individual trees on areas of steep slopes. On the flatter areas, build small beds and fill them with rich topsoil for flowers or vegetables and herbs, if desired. The best approach is to use a single material for all walls, stairs and beds and weave them together into a single design.