It happens twice a year and is seen by millions of people at each occurrence, but it has had little notoriety until very recently when it received its name - "Manhattanhenge."
It's the time of the year when the sun sets in perfect alignment with the east-west cross streets in midtown Manhattan, illuminating every street for the last 15 minutes or so of daylight.
So pay attention, locals and visitors, on July 11/12 for this astro-urban delight (which also occurred May30/31) .