Actually it’s a good thing, but the angle of this image makes it look kind of post-apocalyptic:
Looming over Green Park, it’s an eight-story antigravity forest composed of 12,000 plants.
Patrick Blanc uses a kind of techno-trellis as the underlying structure: A plastic-coated aluminum frame is fastened to the wall and covered with synthetic felt into which plant roots can burrow. A custom irrigation system keeps the felt moist with a fertilizer solution modeled after the rainwater that trickles through forest canopies.
But plants for this vertical landscape must be chosen with care. Because the walls are so high, conditions vary widely. The shade at ground level is perfect for rare Asian nettles; on the brighter upper stories, plants that usually cling to windblown cliff faces brave the blustery British breezes. (Wired Magazine)
I actually think the underpass wall design is a great idea for urban areas. So long as cities promise to keep the walls watered, I think it would improve air quality and aesthetic quality.