Let there be light! Not only is that a call from the divine, but it’s also the cry from inner-city residents.

A city plan to rezone the heart of Manhattan has touched off a new campaign to protect the afternoon light falling on a beloved park that offers honey locust trees, azaleas, pansies and a seven-metre-high waterfall. It is a lush oasis in a neighbourhood starved for green space.

The foundation that runs the park, on East 51st Street between Second and Third avenues, says the rezoning would allow taller buildings that could block its afternoon sun, endangering the plant life and making the spot colder, darker and far less inviting.

Even Australia is not immune with concern in Melbourne and the Gold Coast that the high rise building boom will cast intrusive shadows.

But with apartment living becoming increasingly popular in Australia as people embrace the advantages of urban living, architects are looking at ways to minimise the impact of shadows to keep cities liveable.

About 250 skyscrapers are slated to redraw London’s skyline in the near future—each with its own dark imprint on the streets below. So architects at the firm NBBJ in London decided to see if they could come up with an entirely shadowless building. They used computer modeling to design a pair of buildings, one of which works like a gigantic, curved mirror. The glass surface of the northernmost building reflects light down into the shadow cast by its southern partner. And the carefully defined curve of that glass allows the reflected light to follow the shadow throughout the day. Note that the reflected light is diffuse—not a focused death ray that could fry an egg or burn tourists. “The relationship between the sun and shadow is the relationship between the two buildings,” says Christian Coop, NBBJ’s design director.

To come up with that shape, the architects entered various building requirements—like footprints for office and living space—into design software called Rhinoceros. Then they told the program to generate designs that maximize the light reflected onto the ground.

Sydney’s One Central Park has moveable mirrors that reflect light onto shaded areas below or block the sun during the hot summer.