On 99th Street between First and Second Avenues in Manhattan, just a few blocks from some of the city’s most palatial homes, the air is tinged with a certain sourness. There, there is a Sanitation Department garage where giant orange trucks snooze in a dark ground-floor space. More than a dozen white garbage trucks sit in rows outside.

This two-story brick building is nothing special, even a bit decrepit, but as you walk up its crooked metal staircase toward the second floor, you will find the first hint that something wholly different, even a little dazzling, hides amid all that dingy gray: there it is, on the right, a painting of perky pink flowers on a Big Bird-yellow background hanging in the stairwell. It looks like the sort of thing that should hang on a nursery wall. And in fact, it probably once did.

The second floor of this garage, long deemed too weak to support vehicles, has become a gallery of sorts, home to hundreds and hundreds of paintings, photographs, posters and objects, neatly framed and mounted on the walls. They are varied in every way — from style to age to material — except for one: almost every last piece of the collection was rescued from household trash by New York City’s sanitation workers as they went along their daily routes.

Over here is a portrait of a grumpy-looking Winston Churchill, and over there, a very nice pastel copy of Henri Matisse’s “Woman With a Hat.” There are photographs of the Brooklyn Bridge; landscapes done in watercolor; ancient tricycles and toy trucks; and four electric guitars, one without pickups, another without strings, arranged around a Michael Jackson poster and gold-sequined tie. There is even a Master of Business Administration diploma from Harvard hanging by a window.