Driving by most parking garages is a thoroughly unremarkable experience. Driving past the parking garage at Eskanazi Hospital in Indianapolis, however, is akin to visiting an abstract art museum: as of June, its facade has been decked out with a fluttering wave of 7,000 yellow and blue panels that, depending on your angle, change patterns and saturation.

Eskanazi first opened in 1850 to treat Smallpox. That particular epidemic has long been put to rest, but the hospital remains, and for years now has incorporated art and greenery into its approach to wellness. After a recent expansion the hospital commissioned 16 artists to create new pieces varying in scale, the largest of which is this parking garage facade by Los Angeles-based design firm Urbana. “As with any expansion there’s an enormous parking requirement, and [the hospital] was aware from the beginning of the aesthetic challenges parking garages pose. So I was thinking about camouflage, and how we can cover up the cars on the inside,” says Rob Ley, founder of Urbana and the architect-turned-public artist who masterminded the installation.

Oftentimes, Ley’s work is designed to react to movement or the people around it—one sculpture and light installation in Los Angeles is activated by the movement of underground trains. But the Eskanazi piece had a more delicate set of constraints: It would need to last several decades, and be able to withstand icy Indianapolis winters. Rather than rely on electricity, Ley based his designs off lenticular pictures that create the illusion of a changing, three-dimensional image when tilted from side to side. With the help of custom-written software, Ley was able to figure out how to position the 7,000 aluminum panels—that only come in two colors—so that the hue and pattern of the parking garage facade would morph as passengers go by. “You can make something that’s interactive not by having the building or the pieces move, but because you have the people looking,” he says of the trompe l’oeil.

May -September, as the installation is called, was inspired by the region environment-specific project. Ley grew up near Indiana, in Illinois, and can remember how green it is in the spring and summer, and then how gray it can be during the winter months. To guarantee passersby wouldn't miss the Eskanazi parking garage facade, he chose two colors that would be sure to contrast with the land: royal blue and a marigold yellow. The hospital's budget wouldn't allow for different shades of blue and yellow, so Ley relied on the position of the sun to create the affect of darker colors, and thus the patterns seen from a distance. Watching the panels is like looking at clouds: At a glance, they resemble a football stadium full of fans. At another, they create an abstract topography. "It's what I call a 'tattoo effect,' " Ley says. "If something is so literal, after five or ten years you'll think, 'Oh, that thing still.' If something is open ended enough, you won’t get tired of it."