From an NY Times article on pet-centric design:

About the walkway:
“When I had cats growing up, they were always able to go outside,” said Bill Hilgendorf, 30, who lives in Brooklyn with his wife, Maria Cristina Rueda, also 30. “We felt a little guilty having our cats confined to a relatively small apartment space.”
A late-night cat food commercial inspired the couple, who are furniture and graphic designers, to build a bright yellow staircase that runs along one wall, over a doorway and above the stove, where it meets the kitchen cabinets. The piece — made from a four-by-eight-foot panel of fiberboard, cut into seven-inch-wide strips with remnants of industrial carpeting on top — took a weekend to build.
“We wanted to make something that was a design element, but didn’t take over the space,” Mr. Hilgendorf said. “We painted it yellow, because we wanted it to be an architectural element. But it’s also very narrow, so it doesn’t encroach on the room too much.”
They weren’t sure if their cats, Miles and Attila, would actually use it, he said, but it didn’t take long for them to turn the addition into their own personal jungle gym. “At night they do this loop,” he said. “They run up and then jump down onto the refrigerator and chase each other around.”