From Gothamist:

Manhattan-what? Here, let's let the director of the Hayden Planetarium explain:

"Next Sunday and on July 13, the sun will fully illuminate every Manhattan cross street (not the curved or angled ones) on the street grid during the last 15 minutes of daylight, and it will set on each street's center line. The sight is breathtaking."

You know, of course, what the longterm effect will be? Centuries from now, puzzled archaeologists will conclude that ancient Manhattanites worshipped the sun; devotion was displayed in the common "Mystic" tans, and the city was laid out on a celestial grid. The festival known as "May Two-Four-Plus-Four" was the holiest of days.

Of course.