Twice a year, if it's not too cloudy, the sun famously sets west of Manhattan's skyline in such a way that the island's cavernous east-west streets (OK, they're tilted on a slight axis) flood with light. The sun itself appears to dip to the horizon directly between the skyscrapers. Anyone with a camera is forgiven for halting traffic. Locals call the event Manhattanhenge, a rare alignment of astronomy and urban planning.
Like most cities, though, New York is composed of numerous interlocking street grids, neighborhoods all plotted on a slightly different axis depending on the lay of the land or the whims of earlier settlers. This means that there are technically "henge" days (although we don't think anyone calls them that yet) across the city at different dates on the calendar. And now the mapmaking company CartoDB has built a phenomenal tool using OpenStreetMap to find them, casting the city's street grid in, err, "a whole new light."