Giant Sand Castle – South Ferry
2 New York Plaza near Whitehall Street
On view through Monday, August 12
This is no ordinary sand castle. Sand sculptor Matt Long's super-detailed 16-foot-tall creation really stands out, especially since it's sitting in the middle of downtown Manhattan. When we visited, the structure was still in progress but we could still see how awesome it was going to be. We plan to go back to see the finished castle before it comes down on August 12.

No Limits – Downtown Manhattan
Flatiron Plaza, 23rd Street and Broadway
Union Square, Broadway and 18th Street
Baruch College, 25th Street between Lexington and Third Avenues
On view through Sunday, August 18
Three pieces from No Limits—Alexandre Arrechea's cool series of contorted NYC skyscrapers that were on view earlier this year on Park Avenue—are now on display in three Downtown Manhattan plazas. I saw them the first time around and they're even more impressive now that you can get up close to them to see the details. Afterward, romp around the playgrounds in Madison Square Park or Union Square Park—both are nearby.

Red, Yellow and Blue – Flatiron
Madison Square Park, 23rd Street at Madison Avenue
On view through Sunday, September 8
New York City artist Orly Genger knotted and painted 1.4 million feet of nautical rope scavenged from the Eastern seaboard to create this eye-popping installation in Madison Square Park. The work snakes throughout the green space and features high walls and circular chambers. The undulating hills are so inviting it's tough to keep the kids off them. But try: Touching isn't allowed. Kids need something more interactive? The Madison Square Park Conservancy is hosting a free family art workshop inspired by the exhibit on Saturday, July 27.

Lotus – Union Square
Union Square Park, Union Square East and 15th Street
On view through October
Although Jaehyo Lee’s structure made from Korean big-cone pine is meant to resemble a giant champagne flute, my son and I both thought it was a giant ice-cream cone. Afterward, grab some actual ice cream at nearby Smush and burn off the sugar rush in the Union Square Park playground.

Paley on Park Avenue – Midtown East
On view through Friday, November 8
Park Avenue Malls between 52th and 67th Streets
This series of 13 enormous steel pieces by renowned sculptor Albert Paley are impossible to miss—some are up to 21-feet-high and 40-feet-long! Meant to evoke the vibrancy and action of NYC, the abstract sculptures are huge and intimidating but are best appreciated up close. They're quite intricate.

Dancers of the Wind – Lower East Side
East River Park Promenade
On view through November 2013
This trio of brightly colored dancers is located on the East River just south of the East 10th Street footbridge. From afar, they seem to move in the breeze but as you get closer you realize they're made of metal and not likely to be swayed. It's an enchanting illusion. Afterward, head to nearby Tompkins Square Park, where you'll find a mini pool and two playgrounds.

Hosea – Midtown East
Tramway Plaza, 59th Street and Second Avenue
On view through Sunday, December 1
Carole Eisner's 15-foot-tall sculpture dominates the small green space outside the Roosevelt Island tram station. Inspired by the mechanics of the tram, the steel and iron structure features a giant train gear atop a massive tripod with wavy legs. It's so big kids can even crawl under it. Afterward, hop the tram and explore Roosevelt Island.

Lightness of Being – Financial District
City Hall Park, Broadway and Chambers Street
On view through Friday, December 13
The 11 contemporary works in this Public Art Fund installation celebrate playfulness, though some are more whimsical than others. Daniel Buren's kaleidoscopic "Suncatcher," which casts colorful patterns on the ground, is definitely the most eye-catching. But we were partial to James Angus' replica of a skewed John Deere tractor. Olaf Breuning's "The Humans" consists of six goofy figures that represent a kind of cartoon human evolution. And then there's Ugo Rondinone's truly strange "dog days are over," a so-called performance piece featuring a hobo clown who sleeps on a bench all day. Happily, much more lively musicians often frequent the park.

Bonus: The vintage French carousels and carnival attractions at Fête Paradiso aren't exactly public art but they are gorgeous and well worth looking at—and riding on!

Find out about other free seasonal activities in our Summer Fun Guide.