Here is a green wall I easily and inexpensively constructed from recycled materials.
The wall is four feet wide by five feet tall and fashioned out of rigid recycled plastic milk jug crates for the rear and side structural support.
The growing media is mineral wool and the celtic cross cut from old copper gutter sheet.
The Florida Green Anoles absolutely love it, providing them with habitat to escape the larger exotic predators here, the Cuban anoles.
Bringing Urban Green back to the cities doesn't have to be complicated and require high tech materials engineering or mechanical systems.
Recycled material technology is a sustainable approach to take when implementing Urban Green.