A project started Wednesday to reinforce the ruins of a 3,000-year-old city on the ancient Silk Road in northwest China's Xinjiang Uygur Autonomous Region.

The project marks the beginning of a comprehensive protection plan for more than 20 key historical sites along sections of the Silk Road in Xinjiang. Investment for these projects is estimated at 420 million yuan (US$52 million).

Workers will use rivets to consolidate the earthen walls of the ruins in Jiaohe City, located in a valley 13 kilometers from Turpan in eastern Xinjiang, according to Dunhuang Academy's technological service center for cultural relics conservation, an institute based in neighboring Gansu Province.

Ancient Jiaohe City was the capital of the State of South Cheshi more than 3,000 years ago. The city is about 1,650 meters long and 300 meters wide. It was destroyed during a war in the 13th century. The ruins of the city are among the world's oldest and best-preserved adobe buildings.

However, the dry and sandy weather in the region posed a threat to its protection.

Consolidation project in Jiaohe City will cost about 70 million yuan (US$8.75 million) and last for three years.