Today we're discussing urban planning and the role of green spaces. Many cities have introduced rooftop gardens, but a recent study in Melbourne found that vertical gardens on building facades are more effective for reducing heat. Unlike rooftop gardens, which require structural reinforcement, vertical gardens can be attached to existing walls and also improve air quality at street level. However, they need regular irrigation systems. The study suggests that combining both approaches could lower city temperatures by up to 3 degrees Celsius, but only if maintenance costs are shared between property owners and local councils.