Look on the north side of 49th street between 2nd and 3rd avenues (close to 3rd) for the cast iron gates that can, but usually don't, close off the narrow carriageway into the yard.
It was originally sculpted (out of a mishmash of buildings and open space) by designer James Amster at the end of the Second World War. He envisaged an artists' colony, and Isamu Noguchi created several works here.
The Instituto Cervantes (a Spanish government-sponsored cultural center) occupies most of the buildings around the Yard. They redeveloped the site in 2001/2.
It's a public space but is often deserted.
Find Amster Yard on our Midtown Concierge Map at grid reference C4 - Clive Burrow