IN one of Washington Irving’s tales from “The Alhambra,” the short-story collection that rooted the great 14th-century Moorish landmark in the American imagination, a poor Spaniard and his daughter discover a hidden chamber deep within the abandoned palace’s crumbling walls and spirit away the treasure inside.

Over the last three years in a suite of galleries concealed from public view on the second floor of the Metropolitan Museum of Art, it is as if Irving’s fable of Islam’s rich past has been unfolding in reverse. Treasures, in this case more than a thousand pieces from the museum’s extensive holdings of Islamic art, have been slowly populating newly constructed rooms, taking their places in gleaming new vitrines with Egyptian marble underfoot and mosque lamps overhead, amid burbling fountains and peaked arches framing views of 13 centuries of art history.

When this 19,000-square-foot hidden chamber is finally opened to the public on Nov. 1 with the unwieldy but academically precise new name of the Galleries for the Art of the Arab Lands, Turkey, Iran, Central Asia and Later South Asia, it will not only represent the culmination of eight years of planning and work. The reinstallation and enlargement of the collection — one of the most important outside the Middle East — also promises to stand as a watershed moment in America’s awareness of the visual culture of the Islamic world, at a time when that world looms as large as ever on the international stage and in the American psyche.

Over the last year and a half the museum allowed a reporter to watch the galleries come into being, as bare brick walls were slowly transformed into visions of ninth-century Baghdad, medieval Iran and early Islamic India, and as the museum found itself in a transformed position. It had long harbored ambitions to put its Islamic holdings in a bigger spotlight. But it had little idea when it began rethinking the galleries almost a decade ago that it would be doing so against such a culturally loaded backdrop: the American military presence in Afghanistan and Iraq, the escalating tensions with Iran and the outbreak of the Arab Spring. For an institution that seems to exist as a sanctuary from geopolitics, and often operates in isolation from them, the project became a delicate diplomatic as well as curatorial undertaking.