From the Colosseum, cutting across the ancient racecourse Circus Maximus, it is a wonderful stroll up the Aventino, one of Rome's seven hills, home to a dreamily upmarket residential district with deep-green trees shading its orange-ochre buildings.

BBC: A perfect day in Rome

Called Zone Green, it will promote energy efficiency by making it easier to add photovoltaic panels, wind turbines, greenhouses and shading devices to the roofs and sides of older buildings.

WSJ: Zoning Laws Grow Up | By Julie V. Iovine