Many residents of, and tourists going to, Xi'an have recently noticed that the Bell Tower and the ancient city wall, both among the most popular destinations in the capital city of Northwest China's Shaanxi province, are under renovation.

The Bell Tower has especially attracted the attention of many with a net covering its surface. Some witty internet users say that the historic landmark, built during the Ming Dynasty (1368-1644), is "wearing a face mask".

According to a notice released by Xi'an Bell and Drum Towers Museum, the Bell Tower suspended services from June 10 to Aug 25 for renovation.

Wang Lei, director of the museum, tells China Daily that as a precious historic heritage site, the Bell Tower undergoes frequent renovation. The last overhaul was in 2011 and the renovation this year is a relatively small project, which will last for only two and a half months and focus on the restoration of the roof and the rafters.

"Some of the gold foil on the roof of the tower has fallen off and rafters have decayed because of weathering," he says. "It's a regular renovation and protection project funded by the National Cultural Heritage Administration."

Only a few kilometers away from the tower, restoration continues on the ancient city wall of Xi'an, which dates back to the Ming and Tang (618-907) dynasties.

Experts on the preservation of historic relics have to diminish the decaying caused by alga and mycete (fungus) on the surface of the city wall regularly, so that the wall is not damaged.