With one’s eyes closed, Beijing’s main roads sound like any Chinese city. All around is the roar of traffic, featuring recorded safety warnings from buses and the occasional bell of a rental-bicycle. But in the capital’s last hutongs, as its ancient grey-walled alleys are known, fragments of an older soundscape can be heard.

The song of caged crickets is one. Hung in the doorways of courtyard homes, the insects bring a rural note into the city. A quarter-century ago their song was common.

Another relic is the musical sound produced by steel plates, announcing a knife sharpener’s arrival. Several such specialists still work Beijing’s streets. Their sounding-plates attract customers from hutong homes and high-rise flats. But numbers are falling.

An almost-vanished Beijing sound is one of the strangest. Like the noise of flying saucers in an old science-fiction film, it is made by pigeon whistles. Tiny flutes made from bamboo, these are sewn into the tail feathers of pigeons kept in rooftop cage. The birds are released twice a day to circle in the sky. Even 20 years ago, it was possible to hear this melodic noise in the hutongs.

Modern Beijing is a city in a hurry. Many hutongs have been torn down to make way for wide avenues and shiny skyscrapers,   leaving no room for pigeon lofts(鸽舍). Zhang Baotong is one of Beijinig’s last master pigeon-whistle makers. He is advising a museum of sound in Songzhuang, a suburb of Beijing that is popular with artists. A rooftop cage is planned, with more than 100 pigeons that will take to the skies for visitors.

The co-founder of the museum, Colin Siyuan Chinnery, is a British-Chinese artist and collector of Beijing’s sounds. He lists the rattles(拨浪鼓) and rhythmic cries used by fortune tellers and medicine sellers, doctors, barbers and knife sharpeners. Many of these will be showcased in an exhibition about old Beijing narrated by an animation of Mr. Zhang. Other places had traders’ cries, but true Beijingers dismiss sellers elsewhere as mere loud shouters; Beijingers’ pride is one tradition that never fades, Mr. Chinnery says.

Carved into the cliffs above the Dachuan River, the Mogao Caves, south-east of the Dunhuang oasis, Gansu province, contain the largest, richest, and longest used treasure house of Buddhist art in the world. It was first constructed in 366 AD and represents the great achievement of Buddhist art from the 4th to the 14th century. Four hundred and ninety-two caves are presently preserved, housing about 45,000 square meters of murals (壁画) and more than 2,000 painted sculptures. Cave 302 of the Sui Dynasty contains one of the oldest and most vivid scenes of cultural exchanges along the Silk Road, showing a camel pulling a cart typical of trade missions of that period.

As evidence of the evolution of Buddhist art in the northwest region of China, the Mogao Caves are of unmatched historical value. These works provide an abundance of vivid materials depicting various aspects of medieval (中世纪的) politics, economics, culture, arts, religion, ethnic relations, and daily dress in western China. Many of these masterpieces are creations of an unparalleled aesthetic (美学的) talent.

The discovery of the Library Cave at the Mogao Caves in 1990, together with the tens of thousands of manuscripts and relics it contained, has been acclaimed as the world’s greatest discovery of ancient Oriental (东方的) culture. This significant heritage provides invaluable reference for studying the complex history of ancient China and Central Asia.

The Mogao Caves were included on the World Heritage List in 1987. At the state level, China has put all World Heritage Sites under top-level protection. In 1961, the Mogao Caves were listed as one of the State Priority Protected Sites by the State Council and were put under the protection of national laws, including the Law of the People’s Republic of China on the Protection of Cultural Relics. The Administrative Institution of the Mogao Caves has been cooperating with international counterparts (同行) to study conservation and site management and looks forward to continuing its work in preserving the heritage of the site.

More than 10 million Chinese cultural relics have been lost overseas, lots of which were stolen and illegally shipped out of China during the times of war before 1949. About 1.67 million pieces are housed no more than 200 museums in 47 countries, which accounts for 10 percent of all lost Chinese cultural relics, and the rest are in the hands of private collectors.

Most of these treasures are owned by museums or private collectors in the United States, Europe, Japan and Southeast Asian countries. There are more than 23, 000 pieces in the British Museum, most of which were stolen or bought for pennies more than 100 years ago.

The major method to recover these national treasures was to buy them back. In some cases, private collectors donated the relics to the government. Also the government can turn to official channels to demand the return of relics.

In 2003, a priceless bronze pig’s head dating from the Qing Dynasty was returned to its home in Beijing after it was removed by the Anglo-French Allied Army over 140 years ago. Macao entrepreneur (企业家) Stanley Ho donated 6 million yuan to buy it back from a US art collector and then donated it to the Poly Art Museum in Beijing.

Although buying-back is the most feasible way to recover the lost treasures, limited funding is always a big headache.

In recent years, the Chinese government has improved efforts to recover the precious cultural relics lost overseas. It has started a national project on the recovery of the treasures and has set up a database (数据库) collecting relevant information. It has signed several international agreements with many countries on this matter, and is also looking for international cooperation to recover the relics by working closely with several international organizations.