The Xi’an City Wall is the most complete city wall that has survived China’s long history. It     1     (build) originally to protect the city     2     the Tang dynasty and has now been completely restored (修复). It is possible       3     (walk) or bike the entire 14 kilometers.

We accessed the wall through the South Gate. The wall is 12 meters high and from here you can see streams of people moving inside and outside the City Wall.

After     4     (spend) some time looking at all the defensive equipment at the wall, we decided it was time for some action and what     5     (good) than to ride on a piece of history!

We     6     (hire) our bikes from the rental place at the South Gate. My bike was old and shaky     7     did the job. It took us about 3 hours to go all     8     way around the Xi’an City Wall. Supposedly you can do it in two hours, but we stopped at the different gates and     9     (watchtower) to take pictures or just to watch the local people going about their     10     (day) routines.

China's national observatory on Monday issued a yellow alert for sandstorms in the northern part of the country. “    1    （start）from Monday to 8 a. m. Tuesday, affected by cold fronts and heavy winds, floating sand and dust       2    （expect）to sweep parts of several northern provinces and the city of Beijing,”     3    （forecast）the NMC.

Some regions in Inner Mongolia, Ningxia, Shaanxi and Shanxi were hit by strong sandstorms. The capital Beijing was enveloped in yellow dust     4     Monday morning with visibility at less than 1 km,     5     followed an official yellow warning for the sandstorm. The sandstorm is the strongest and the most sweeping     6     in nearly a decade. Remote sensing images of dust in northern China show the dust from Mongolia     7    （gradual）traveled south with the airflow.

This wave of sandstorms is a result of the combined       8    （effect）of cold air and cyclones from Mongolia. “The combined action of the Mongolian cyclone and the cold high     9    （press）provided a strong impetus（动力）for the sandstorm,” said Zhang Bihui,     10     senior engineer with the NMC.