Northwest China's historic city of Xi'an - famous for its buried army of terracotta warriors, its mosque, its pagodas and its splendid city walls - has begun building its first subway line, in an effort to ease traffic congestion in the city and protect its famous cultural sites.

Construction of a 1,450-meter test section of Xi'an's No. 2 subway line started on Friday. The line from Zhangjiapu to Youjiazhuang in northern Xi'an will take 30 months to build at a cost of 270 million yuan (US$33.7 million).

Construction of the rest of the 26.4-km No.2 subway line will begin in the second quarter next year, according to the Xi'an Subway Construction Headquarters Office.

No.2 subway line, which links North Railway Station to Weiqu in the south, has 20 stations and is expected to open in 2011, said the office. The line will cost a total of 9.78 billion yuan (US$1.2 billion ).

No. 2 subway line will be built 20 meters underground to protect a 13.7-kilometre city wall dating back to the early Ming Dynasty (1368-1644), a key downtown heritage site, according to the office.

The line will carefully circle an ancient tower building. Advanced technologies will be used to protect ancient buildings from the impact of tremors and shaking.

To preserve its historic sites, downtown Xi'an restricts interchanges and elevated roads, which means that ground traffic is increasingly congested.

A construction plan approved by the State Council provides for six subway lines with a total length of 251.8 kilometers.

The city will build the 50.3 kilometers of No.1 and No.2 subway lines in the period 2006-2015. Construction of the east-west No.1 subway line will begin when No.2 line is almost finished.

Beijing, Shanghai, Tianjin, Guangzhou and Shenzhen all have subways. A number of other Chinese cities are building or plan to build subways.

(Xinhua News Agency September 30, 2006)