Christo's new project, the “Floating Piers” is open until July 3. It comprises two miles of marigold-yellow walkways bobbing atop the waters of Lake Iseo, a small lake in northern Italy, connecting the waterside town of Sulzano with two small islands.

It took 22 months and up to 700 people to build it.

The pathways are supposed to let visitors feel like they're walking on water. Sulzano expects about 40,000 people a day to visit.

Marinas often use temporary, floating piers; a common technique involves propping them atop styrofoam cubes. “We discovered very soon that this cube system was perfect for us,” says Wolfgang Volz, Christo’s project manager.

Christo's team had to build their own cubes. Then he, Volz, and a few dozen workers started connecting the cubes into 50- by 330-foot sections. They attached the cubes with giant screws, right on the water, in a corralled section of Lake Iseo, which you can see here.

The Floating Piers use 220,000 cubes in total.

The fabric that covers the styrofoam is an absorbent nylon that Christo sources from a German supplier.

It’s not waterproof—people would have slipped in puddles, a non-starter for a walk-on-water art installation with no guardrails.

That porousness also lends the pathways some color-changing charm: “When it’s wet it’s almost red,” Volz says. “And when it’s dry it’s totally yellow, almost lemonade yellow.”

Divers helped to both secure the floating cubes to concrete anchor weights, and the fabric to the walkway, with extra-strength carabiners.