Hundertwasser Art Centre, Madison Square Garden - exemplars of the rooftop revolution

Sheep in a small rooftop farm in Munich. Photo / supplied

Using the roof of a city building for something fabulous is a very old idea. The Hanging Gardens of Babylon made it famous 2500 years ago. Madison Square Garden, at the turn of the 20th century, had the largest rooftop restaurant in New York as well as a garden cabaret. And yet most cities still don't do it very much. By one estimate, roofs cover up to 35 per cent of urban land but only 2 per cent of rooftops are in use.

Still, there's a quiet revolution underway. Rice paddies at Thammasat University in Bangkok form Asia's largest organic rooftop farm, supplying food for 135,000 meals a day. You can grass-ski down from the roof of a power plant in Copenhagen and watch open-air movies on rooftops in many cities, including New York, Los Angeles, Houston, San Diego and London.

In Hamburg, subsidies are available if you want to plant your roof. In Cairo and Alexandria, there's a programme to teach low-income families hydroponic rooftop gardening: it feeds them and gives them a stable source of income.

Rooftop rice fields, Thammasat University in Thailand. Image / supplied

The environmental benefits are clear: rooftop parks and gardens help purify polluted city air and capture carbon dioxide. For the past 11 years in Toronto, all new commercial, institutional, residential and industrial buildings larger than 2000 sqm have been required to cover between 20-60 per cent of their roofs with green space. Flower meadows are popular.

In other cities you can find rooftop vegetable allotments, tiny homes, community workshops and butterfly gardens. In Singapore, an urban farm on top of a shopping mall provides food for the restaurants within.

There's an art installation on a rooftop in the Austrian city of Linz that aims to create "a friendly, yet unknown world", something that is "physical and meditative at the same time". The whole thing is a kind of labyrinth made from billowing red fabric - but don't worry, apparently there's a safe space in the middle.

Lots of cities have rooftop golf. And in Munich, on top of a building full of startups and creative enterprises, they're farming a small herd of very woolly sheep.

In Whangārei, the new Hundertwasser Art Centre has its own rooftop garden. Gorgeous art inside, too.

Rooftop hydroponics in Cairo. Photo / supplied

Concept illustration of tiny homes on a rooftop in Rotterdam. Image / supplied

Design for Living is a regular series in Canvas magazine.