PHOENIX - The Burton Barr Central Library in downtown Phoenix is an architectural marvel, but you may not truly know that until the exact moment of the summer solstice.

The top floor, designed by architect Will Bruder, is built so that, at the peak of summer solstice, the sunlight comes in through all the skylights and illuminates the library.

It's a place, the library describes, where "man-made engineering collaborates with the sun."

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This year, the library is celebrating the start of summer with music, an appearance by Bruder and much more from 11 a.m. to 4 p.m.

The visual phenomenon is expected to occur at solar noon (12:30 p.m.), according to the library.