As workers busily finished construction of the brand-new train station Grand Central Madison in November, artist Kiki Smith was standing in front of her new mosaic "River Light,” an abstracted, blue-and-white depiction of glinting sunshine on the East River.

"I’ve never made a mosaic before,” she says, pausing to touch the varied surfaces of the small and colorful glass pieces making up the composition. She adds, "I’ve also never made anything so big in my life.”

The 80-foot-long work is on the Madison Concourse level of Grand Central Madison, the 700,000-square-foot, $11.1 billion Long Island Rail Road terminal set to open in December. The terminal is the Metropolitan Transportation Authority’s largest project yet.