Great museums contain far more art than they could ever show. The Met's collection has more than 1.5 million objects, and only about 4 percent of them are on the walls on any given day. The rest sits in storage, catalogued but almost never seen.
Some collections expose an API that will tell you which works are not currently on display. This is a small machine that asks for those. Hit refresh and it fetches a random piece that is sitting in storage right now at the Met, the Cleveland Museum of Art, London's Victoria and Albert, or the Getty. Let this be the gallery that never was.
Credit for the idea goes to a note by Will Wang, who had a similar idea using the Art Institute of Chicago's API. The post hit the front page of Hacker News and not long after, the Art Institute became overwhelmed with requests and moved their image servers behind a bot wall, breaking the demo. Perhaps some beautiful things thrive best in obscurity.