While Harvard professor Gulru Necipoglu was doing research in 1986 at Istanbul's Topkapi Palace Museum Library, curator Filiz Cagman produced a scroll she thought might be of interest to the visiting scholar. The two women had become friends over the years, and Cagman had read an article by Necipoglu on early Islamic architectural ground plans. "Look," said Cagman, "I have something similar to that material." As they unrolled the 30-m scroll and its sophisticated geometric patterns emerged, Necipoglu remembers, "I was amazed because I had never seen anything like it."

Nor had anyone else. The well-preserved document of heavy rag paper is a rare artifact from centuries past. The scroll, with its 114 drawings, is a pattern book from the workshop of a master builder who worked in Persia during the late 15th or 16th century. It is the earliest of its kind to have been found intact. Before its discovery in Istanbul, the earliest known Islamic architectural scrolls were fragments from the 16th century around Bukhara, Uzbekistan. The fascinating find is now reproduced in an elaborate modern book with a scholarly analysis by Necipoglu: The Topkapi Scroll: Geometry and Ornament in Islamic Architecture (395 pages; $160), published by California's Getty Center for the History of Art and the Humanities. The tome has won an award from the U.S. Society of Architectural Historians and was named the best new scholarly book in the field of architecture and urban planning by the American Association of Publishers.

Born in Istanbul, Necipoglu, 40, has lived in the U.S. since 1975 and studied Western art history as an undergraduate at Wesleyan University. "Frankly, I took Islamic art for granted," she says, "until a college adviser suggested that I look into it." In 1979 she entered Harvard as a graduate student, and she later attended Columbia University. Two years ago, Harvard named her to the prestigious post of Aga Khan Professor of Islamic Art. After digging through archives, she determined that the Topkapi scroll, dating from the Timurid or early Safavid dynasties, which ruled in what is now Iran, had probably been put together in Tabriz, a city known for its decorative and architectural splendor.

Such working drawings were part of a widespread tradition in medieval Islam, but since they were usually not secured in archives, most have been damaged or lost over the centuries. Still, Necipoglu believes that some may yet exist in the hands of traditional practicing masons who guard them jealously and pass them on as a family secret. The Topkapi scroll ended up in Istanbul almost by accident. At the Ottoman court, the elaborately patterned tile and glazed-brick of the Timurid style was briefly the vogue, and Persian tilemakers were imported to carry out those designs. The scroll, which is a kind of how-to manual for the decoration of flat panels and elaborately ornamented vaults, must have been left behind and deposited in the imperial treasury after the patterns were no longer fashionable.

The text accompanying the scroll's two- and three-dimensional ink drawings deepens the significance of abstract design in the medieval Islamic world. Well into the 20th century, the West viewed much of Islam's abstract art as merely decorative. The 19th century French writer Jules Bourgoin, for example, after studying the great buildings of Moorish Spain and North Africa, decreed that the importance given to surface decoration was a sign of inferiority. But as Necipoglu demonstrates, the abstract designs, generally referred to as "arabesques," have not always been central to Islamic art, which is richly diverse.

Artists were elevated to a privileged status in Islam, Necipoglu says, because "artisanry was not only thought to be the work of the hands but was deeply connected to the creative powers of the mind and therefore was highly valued." God was often compared to an architect, and builders, through their creations, were considered to be imitating the cosmos. The dome of one splendid 17th century mosque was likened to heaven, and its splendid arched galleries to mountains.

Geometry, it was believed, was a gateway to spiritual wisdom--a concept, Necipoglu writes, that helped provide a backdrop for the burgeoning taste for geometric abstraction during the late 10th and 11th centuries. Geometric ornament, she says, "functioned as a multilayered sign system that could be adapted to a wide variety of meanings and context." Repeated patterns--interlocking stars and many-angled geometric shapes--could sometimes act as a metaphor for divine unity. The complexities of color and line dazzled viewers, but beholders were also lifted to another, more profound sphere and awakened to the existence of a harmonious, geometrically arranged universe. A 16th century Ottoman sultan was transfixed by the sight of a lectern covered with multi-angled designs that continually seemed to shift before his eyes as he looked first in one direction and then another. He exclaimed in delight, "God! God! What are these beautiful forms? Like wine, they instantly caused me to lose my head." Made by artists whose names have long disappeared from history, the drawings of the Topkapi scroll retain that same power to intoxicate.