Japanese sunken courtyard illustration

Quick answer：

A Japanese sunken courtyard, also known as a 'kare-sansui' or 'rock garden,' is a traditional Japanese garden design featuring a flat, gravel-covered space. It often includes carefully placed stones, raked gravel, and sometimes small trees or plants. This style of garden is meant to evoke the natural landscape of mountains and rivers in a compressed form, and is a key element in Japanese Zen Buddhism and Shintoism.