Hailing from Australia, Walls was bound to photograph pools. “I was always around pools,” he says. “Also my dad worked for a pool company.” The idea germinated when Walls was on holiday around Bali and Malaysia, then solidified back home in Sydney, when Walls realized he could push his holiday shots to more of an art form.

Top down shots immediately made sense. “When you come in from a top angle, the only thing you’re looking at is the pool,” he says. “Also, there’s a bit of an aha moment with drones from above—it’s like people haven’t seen that view.”

Most of Walls’s photographs are shot straight from above, though few pools are portrayed in full. In one image, the photographer focuses his lens on the sinuous edge of a gigantic wave pool in Sydney, bordered by a sand-colored surface that looks more like a desert mirage than a manmade structure. In another, he captures one half of a minimalist pool in the Joshua Tree National Park, but the eye is drawn to the shadow of a Joshua tree perched from the top right corner of the image. “My thing is to crop down and try and get the best composition I can. How can I take your eyes on a journey—that’s what I’m thinking about,” he says.

For most people, pools are eye candy, but in Pools from Above, they become prime design objects. Some like at the Kaufmann House, designed by the midcentury modern master Richard Neutra, appear as pure rectangle cut-outs with sharp edges and a tiled border. Others harken back to Alvar Aalto’s kidney-shaped pool, oozing with arcs and organic forms. And others, like John Lautner’s futuristic Garcia House, break all norms with a set of wide, terraced steps hugging a striking almond-shaped pool.

Walls spent three years photographing pools around the world, from Sydney to Palm Springs to Mexico City, where he is currently based. About 70% of the photographs that made it into the book were taken on scheduled visits, meaning that the owners were aware that photos were being taken. (In Palm Springs, for example, he noticed the Kaufmann House was on sale, so he scheduled a visit with the realtor.) The other 30% were impromptu shots based on Google Maps sightings, or hard to access places like “elite Airbnbs for magnates,” as Walls puts it.

Is any of this legal, you might ask? “Anything you can see from a plane, you can take a photo of,” says Walls, unless there are people in the shot, which calls for permission. Luckily though, that was rarely a problem—because few people actually live in these luxury houses.