There are many different ways to create layering and depth in a landscape or yard. Retaining walls are one of the best and most durable ways to do this. Some retaining walls are made of wood, some of stone, or blocks; each different material has different benefits, costs, and difficulties with installation, but the end result is undeniable. The real key to a long lasting retaining wall is the installation of crushed rock and a proper drainage system. I built the above wall in mid 2020, its about 100 ft wide and a little under 2ft tall.
Block retaining walls are durable long lasting, but oftentimes a wooden retaining wall is cheaper to install and the materials can also be less expensive, depending on the type of wood used. Pressure treated wood is ideal for ground contact and can be used to create a shape for a raised grass area, and will help to prevent soil erosion if properly install with a drain, as you can see to the right.