敦煌：一个洞被拆成一张世界地图

As the plane approached Dunhuang, there was nothing outside the window but desert.

The first question is a natural one: in a place this dry, why is there a city, and so much art?

The answer starts with water.

Dunhuang sits on the road from the Central Plains to Central Asia, one of the few places along it where you can drink.

With water, caravans can rest; if they can rest, the road stays usable.

If the road stays usable, money and people keep passing through.

The Mogao Caves were cut into the cliff beside that road.

The first cave was opened in 366; generation after generation kept cutting, for more than a thousand years.

Today there are 492 caves with murals, spread across five levels of the cliff.

The murals come to roughly 45,000 square metres, plus more than 2,000 painted sculptures.

In 1987, the Mogao Caves became a World Heritage Site.

Walking into a cave, the first thing you notice is often not the Buddha but the details.

What instruments the musicians play, what carts the caravans use, what people wear, how farmers work the fields.

These images preserve the daily life of Dunhuang from over a thousand years ago.

The people who paid for the caves meant to earn merit, and incidentally left behind a history of ordinary life.

But Dunhuang's most famous story happened in a very small cave.

It's called the Library Cave, cave number 17.

In 1900, the Daoist caretaker Wang Yuanlu was clearing sand when he found a room behind a wall.

When it was opened, more than 50,000 items were stacked neatly inside.

The dates run from the fourth century all the way to the eleventh.

There were sutras, account books, letters, poems, and medical prescriptions.

About a thousand years ago, someone put them in and then bricked up the wall.

Why it was sealed is still unsettled.

What happened next is the real turn in this story.

In 1907, the Englishman Aurel Stein reached Dunhuang.

He bought 29 cases from Wang Yuanlu: about 7,000 complete manuscripts and 6,000 fragments.

He paid 130 pounds in total.

130 pounds, for more than 13,000 items.

The next year the Frenchman Paul Pelliot arrived and spent three weeks selecting in the cave.

He read Chinese, so what he took was mostly the most valuable material.

In 1910, about a fifth of the remaining Chinese manuscripts were shipped to Beijing.

Within ten years, the contents of the Library Cave had scattered across the world.

To study this material today, you have to go to London, Paris, Beijing and many other places.

The contents of one cave were broken up into a map of the world.

It's hard to draw a simple conclusion about this.

Without these men, some of it might already have been lost.

But the way they took it did rest on the other side not knowing.

Both statements hold at once.

Later a compromise appeared, called the International Dunhuang Project.

Collecting institutions in each country photograph their Dunhuang manuscripts in high resolution and put them on one website.

The objects are still spread across countries; the images can be reassembled in one place.

That doesn't settle who owns them, but it does settle the research problem.

The same thinking is applied to the caves themselves.

Murals suffer from damp, from light, and from crowds.

So visits are now capped: you see the digital images first, then the actual caves, with limits on how long you stay.

Moving part of the viewing onto a screen is a way to have the real thing looked at less often.

At dusk I went back to the edge of the desert.

Sixteen hundred years of caves, 45,000 square metres of murals, 50,000 items, 130 pounds.

Put those numbers side by side and you have the whole problem of Dunhuang.

If something will decay where it stands but survives once taken away, which would you choose?