In some cities, parks are replacing asphalt, and city dwellers are suddenly discovering new green space just steps away.
To make cities more livable for an often growing population, government officials, activists and citizens are reclaiming unused or abandoned structures and lots and turning them into new, vibrant green spots that fill the surrounding areas with life.
These 10 examples --- spanning four continents -- are perhaps just the beginning of the concrete-to-green revolution.
Paddington Reservoir In Sydney, Australia
A water reservoir until shut down in 1899, the Paddington Reservoir went on to become a garage, workshop and a commercial garage once more. After sections of the roof collapsed in 1991, the garage was shut down for the last time.
Then architecture firm Tonkin Zulaikha Greer was commissioned for the restoration: They were supposed to cap-off the underground site and build a new arrangement on top.
But the firm fell in love with the ruins and decided to reveal the structure so the public could wander around, says World Architecture News.
Photo: City of Sydney.