Ten miles across the desert from Dunhuang, in an oasis at the foot of the Whispering Sands Mountains, stands a line of eastward-facing caves that make up one of the world's great art treasures - the thousand Buddha grottoes of Mogao.
When Marco Polo rode his camel through Dunhuang in the mid-13th century, Mogao was a flourishing monastery, enriched by the offerings of pilgrims, merchants, soldiers, and other travelers either setting out from, or returning to, China from perilous journeys to the western regions.
Some of the caves were nearly 900 years old when Polo passed their way.
They reflect the two-way cultural exchange characteristic of the Silk Road - China radiating outward its own art, institutions, and civilization, and absorbing in turn religious, cultural, and artistic influences from abroad. The greatest of these external influences was Buddhism.
The caves are hollowed out of a hillside overlooking a trickling stream that is the lifeline of the oasis. There were more than a thousand of them, large and small, but only 492 survive today. They face east so the statues of the Buddha and his disciples will catch the light of the rising sun.
If the statues in the early caves - carved during the Northern and Western Wei dynasties (AD 386-535) - remind the visitor of the archaic smiles favored by early Greek sculptors, it is not surprising.
Buddhism came to China from India through the Greco-Bactrian kingdoms of Central Asia established by some of Alexander the Great's successors. Early Buddhas have the aquiline noses and deep-set eyes one associates with Europeans rather than Orientals.
One of the charms of visiting the Mogao caves is to trace the process of acculturation from Wei and Northern Zhou to Sui and Tang (618-907), when Chinese Buddhist art reached its apogee. Nor is such an exercise irrelevant to the present.
The rulers of the China of today stress that theirs is not a xenophobic nation, as the Europeans who forced open the doors of the celestial empire in the 19th century believed.
Throughout history, communist scholars point out, China has assimilated influences from outside. Although ethnic Chinese form 95 percent of China's billion people, there has always been an interaction between the Han, the ethnic Chinese, and neighbors, north, east, south, and west.
So on the one hand one can trace at Mogao the gradual Sinification of Buddhist art, as faces become fuller, noses less prominent, eyes more almond-like.
On the other, as if to underline the variety of peoples who passed through Dunhuang in Tang times, there are depictions of Persian merchants, Uighur kings, Indian monks, Turkic warriors.
Until the People's Republic came to power in 1949, the preservation of Dunhuang's treasures was lackadaisical at best, and the caves had no doors. Still, the brilliance of blues and greens in the corners of the caves least exposed to sunlight is startling.
All the artists at Mogao are anonymous, from the early Wei craftsmen to the painters and sculptors of the heyday of Chinese art during Tang times. But the subtle gradations of color, the boldness of design, the deft sureness of line are breathtaking.
Soon after Marco Polo's day, the Silk Road declined as the sea route to China was found to be safer and quicker. Polo himself returned to Venice by sea, after 17 years in Cathay.
And the great monastery at Mogao gradually decayed. Still, during the celebrations of Buddha's birthday each April, local people gathered at the caves to offer prayers and gifts.
The Chinese say Mogao is one of several historic sites plundered by Western treasure-seekers. Principal villains on the Chinese list are explorers celebrated by the West as scholars who unlocked the mysteries of the Silk Road - Sven Hedin of Sweden, Sir Aurel Stein of Hungary and Britain, Paul Pelliot of France, Langdon Warner of the United States.
Most of the Buddhist Sutras of Mogao are in the British Museum and other institutions, bought by these and other foreign visitors from the Chinese abbot and Guardian of Mogao early in the 20th century.
Langdon Warner even managed to cut out several pieces of frescoes that were then acquired by the Fogg Museum at Harvard University.
Mr. Warner and others say they were motivated by concern for the preservation of priceless treasures from the hazards of weather and the plunderings of waves of marauders during China's turbulent history.
But the Chinese of today mourn their lost treasures, and their attitude toward the Dunhuang manuscripts and other artifacts in Western museums is similar to that of the Greeks over the Elgin marbles.