Green walls are vertical structures on buildings and other vertical structures. They can be either low-tech built with low resources and low maintenance needs or they can be high-tech and resource-intensive. Low-tech green walls consist mostly of climbing plants that are planted in the soil while high-tech green walls consist of a vertical growing medium, automatic irrigation systems with nutrient supply.

A wide variety of plants can be used to build a green wall such as herbs, grasses, and shrubs in addition to trees growing from the soil. Green walls have multiple benefits such as air purification, noise reduction, and stress reduction. Green walls are typically found in the city centers.