Updated, 8:28 a.m.

Good morning.

Powdery blue skies.

People lazing in the grass, gazing up at the clouds or reading books.

A peaceful melody — John Lennon’s “Imagine” — coming from a tattered piano.

This is not a scene from 1970s New York City; it was this week, beside the fountain in Washington Square Park.

After a nearly six-month rest, the fountain has been turned on for the season. As we slung our feet over its edge yesterday, during what was one of the best days of spring weather yet, we wondered: How, exactly, does this thing work?

The fountain holds almost 32,000 gallons of water between its two tanks, according to George Vellonakis, executive director of the Washington Square Park Conservancy. That water is constantly moving, recirculating between a filtration system (which keeps the fountain clean) and display pumps (with jets that can shoot the water 45 feet into the air).