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Tucked into the hillside behind the Walker Art Center is a downward path, a door, a room. All of it unassuming, at first. But benches beckon. The shape of the place turns your attention upward, to a rectangular opening in the ceiling.

It frames the sky.

Cerulean blue and cloudless one hour, navy the next. You sit, you watch.

"There is no set experience of the work, because the sky is not a set thing," said Pavel Pyś, curator of visual arts at the Walker. "It's an ever-changing portal."

Created in 2005, "Sky Pesher" is one of artist James Turrell's so-called Skyspaces, minimalist installations that toy with light and space and quiet. More than 80 now dot the globe. Other bigger, brighter works in the Minneapolis Sculpture Garden — a giant blue rooster, a giant red cherry — demand your attention.

But "Sky Pesher" coaxes it.

"Time slows down," said Pyś, whose first encounter with Turrell's work, as a teenager, is part of what led him to study art. "It encourages you to really be in the moment, which is something we do less and less as we're constantly scrambling to swipe things on our screens."

This space has hosted weddings and recording sessions. But mostly, it's quiet. Pyś often eats lunch inside, uninterrupted.

That might be because, unlike those other sculptures, "Sky Pesher" doesn't lend itself to selfies. The experience of it can't be captured on a phone or even with words. As the Sydney Morning Herald put it, Turrell's works "are dull to describe but magical to experience firsthand."

Especially at dawn and dusk, when the chamber's artificial light heightens.

"As the interior fills with illuminated color, the infinite sky beyond appears almost within reach," the plaque outside reads. "The artist describes this effect as 'bringing the sky down.' "

That effect peaks at summer's height, Pyś said. "When dusk turns into night, the sky moves through a multitude of colors."

But each season charms. If you happen upon the chamber after it snows but before the grounds crew, you'll find on the concrete floor a perfect rectangle of white.