Twice a year, Chicago is treated to a dazzling display of nature and engineering called “Chicagohenge.”

It’s a solar phenomenon in which the sun rises and sets in perfect alignment with Chicago’s East-West street grid. It happens on the Autumnal (Fall) and Vernal (Spring) equinoxes.

The name comes from Stonehenge, the ancient monument in England (the famous stone slabs line up with the sun on the solstice). In Chicago, the “henges” are the canyons created by the spectacular skyscrapers, which perfectly frame the sun on the solstice.

Every year, photographers from around the world stake out the best spots along the Chicago River and in Millennium Park to try to capture the perfect photograph of the sun bathing the city in a warm orange glow.

Here’s a gallery of some of the photographers featured in our story: ​