Step planting pool example

Quick answer：

A step planting pool is a type of garden feature that consists of terraced levels, each designed to hold plants. These levels can be used to create visual interest and to accommodate different types of plants or plant heights. They are particularly useful in small spaces where vertical gardening is desirable. Step planting pools can be made from various materials such as stone, concrete, or wood, and are often found in Japanese gardens or in contemporary landscape designs.