A collapsible, modular greenhouse, which Design Boom says is "especially suitable for small spaces like cityhouses, balconies, roof terraces or town gardens." What they forgot to mention was that it's especially suitable for growing weed in small spaces.
Related: A few weeks ago, the unfailingly brilliant Michael Pollan wrote an interesting article about the ethics of small, eco-conscious decisions, like growing your own food. If you live in a city and don't have a communal garden, maybe that greenhouse is the answer (after you've harvested your weed).