THE first thing I see every morning is the Cloisters tower, gray and severe, perfectly framed by the living room window of my apartment. The Cloisters, the Metropolitan Museum’s medieval outpost, is about a quarter-mile to the south, on a hill a little higher than the one my building is on, near the stony tip of northern Manhattan. In between is a valley of rooftops, garages and streets. Above, open sky, clouds, the moon, stars.

For 20 years I’ve seen the Cloisters from this vantage, in every season, all weather. The trees of Fort Tryon Park fill out around it in spring, and go gold and brown in fall. In a blizzard the tower, which looks both militant and monastic, softens to an apparition. On cold, clear nights it’s a spaceship poised for flight with a single ruby light, like a bright little planet Mars at its peak, a beacon and warning to planes.

That light is on now as I write, but I won’t be seeing it for much longer. In a month I’m moving to a new apartment, for the usual New York reason: a little more space, in my case for books. I amassed most of my library over the past two decades, though a few things are older, including a sturdy little black-and-white “Guide to the Cloisters,” which I picked on my first visit there, on a pre-Christmas trip to New York City with my family in the early 1960s.

That weekend my sister and I did what a lot of kids did back then on a holiday visit: hot chocolate at Rumpelmayer’s, F. A. O. Schwarz down the street, Scribner’s bookstore, the Rockefeller Center tree. Then there was some adult fare: a look at the new Guggenheim Museum, and an early jazz set at Jimmy Ryan’s, where, mysteriously, my father seemed to know everyone. It was on the way out of the city back to Boston that we stopped at the Cloisters. And what felt to me like a duty call turned out to be an unforgettable experience....