One of the world's rarest maps, a 400-year-old document that shows China at the center of the known world, has been acquired for the James Ford Bell Library at the University of Minnesota. Map enthusiasts have dubbed it "the impossible black tulip of cartography," because of its rarity, importance and exoticism.

The James Ford Bell Trust bought the map for $1 million from a London dealer on behalf of the Bell library. Only six other original copies of the map are known to exist: two in the Vatican, three in Japanese institutions and one in a private collection in France.

"We're thrilled" to get the map, said Ford Bell, director of the American Association of Museums and grandson of the library's founder and namesake. He is a co-manager of the fund that bought the map. "It's great for the library and great for the university."

Drawn in 1602 by Matteo Ricci, a Jesuit priest working with Chinese scholars in what is now Beijing, the six-piece map is 12 feet wide and 5 feet tall. It was carved in sections onto huge blocks of wood and then printed in brownish ink on panels of rice paper like a Chinese folding screen. It shows both North and South America and the Pacific Ocean with reasonable accuracy. China is appropriately linked to Asia, India and the Middle East. Europe, the Mediterranean and Africa also are well delineated.

"There is some distortion, but what's on the map is the result of commerce, trade and exploration, so one has a good sense of what was known then," said Diane Neimann, co-manager of the Ford Bell Trust.

Ricci was the first Westerner to enter Peking, Neimann said, bringing atlases of Europe and the West that were unknown to his hosts. The Chinese had maps of the East that were equally unfamiliar to Western scholars. At the request of the emperor, Ricci assembled a composite map that, among other things, revealed the existence of America to the Chinese, she said.

The map will be unveiled at the Library of Congress in Washington on Jan. 12 and will remain there for three months. It complements the library's famous 1507 Waldseemüller map of the world, which was the first to use the word "America" in reference to the Western hemisphere. The library plans to make digital copies of the Ricci map available to scholars.

After the Washington showing, it will be exhibited at the Minneapolis Institute of Arts, which has an extensive collection of Chinese art and artifacts, before transfer to the Bell library. The Bell library focuses on the development of trade between 1400 and 1800 and includes a lot of Jesuit reports on exploration and commerce in Asia, South and Central America.