Forty important historic sites in the city will be opened to the public for free this weekend as part of weeklong activities to commemorate International Museum Day, which falls on Thursday.

　　In order to prevent the sites from becoming overcrowded, as happened last year, the government will require managers of heritage buildings to strictly control the number of visitors allowed into any site at one time.

　　Tour guides, some of whom can speak English, will escort visitors around the 40 free sites this weekend.

　　"Following last year, the opening of heritage buildings aims to increase the public awareness of understanding and conserving historic buildings," said Tan Yufeng of the Shanghai Cultural Relics Management Commission.

　　Last year, the city opened 23 heritage buildings to the public for free, drawing 46,000 visitors - far more than most of the sites could handle.

　　The city has more than 4,000 cultural sites, mostly historic buildings. The government will also put on a series of lectures at some of its 92 museums from tomorrow through May 25.