Modern Small city Garden

I adore this creation by Modular Garden a small city garden designed on two levels,.

Multiplies the space and the impact of the vegetation.

I would say you need a minimum of 7 meters length to reproduce something similar to this garden.

I also think they could have used the space underneath the second level for storage... 

Small modern city garden created by
www.modulargarden.com 
grasses and bamboos