<p>Fig. 4. <em>Clockwise from top left</em>:&nbsp;A living grass roof in Norway.&nbsp;A stone roof in India.&nbsp;A round roof in Taiwan. Steep, tile roofs in Northern Europe.</p>

Fig. 4. Clockwise from top left: A living grass roof in Norway. A stone roof in India. A round roof in Taiwan. Steep, tile roofs in Northern Europe.

Images courtesy of Nickenge (top left), Biswarup Ganguly (top right), Meiguoren (bottom right), Väsk (bottom left).