The Palace Museum in Beijing is seeking experts' opinion on its first comprehensive plan to preserve the former imperial palace as well as other heritage sites around the compound. The museum on Tuesday revealed its massive conservation plan until 2025. The plan aims not only to step up preservation of the palace, but also its gardens, ancestral temple and altar of land and grain, which are national heritage sites currently being used as exhibition halls, public parks and the top leadership's government compound. The Forbidden City - which refers to the palace as well as the former imperial family's ancestral temple and the altar of land and grain, located to the south of the palace - dates back to 1406. The site was home to more than 20 emperors in the Ming and Qing dynasties until the last emperor Puyi lost his title in 1924. The palace was turned into a museum the following year. The draft conservation plan had been submitted to the State Council for approval, Palace Museum director Shan Jixiang was quoted by the Beijing Daily as saying. The central government was expected to give it the green light by the end of the year, and once approved, the plan would become legally binding, he said. The preservation works would be completed by the end of 2025. "The museum we see today is only a part of the imperial city during the Qing dynasty, which was made up of imperial parks and many other facilities including Jingshan Park, Beihai Park, Zhonghai and Nanhai," said Kong Fanzhi, former chief of the Beijing Municipal Administration of Cultural Heritage. Zhonghai and Nanhai refer to the two lakes in Zhongnanhai, the headquarters of the Communist Party and the State Council. "It is impossible to restore the imperial city because many pavilions and walls were demolished long ago in the course of urbanisation," Kong said. "But the proposed plan is valuable because it raises the idea of the preservation of the whole imperial city." According to the plan, new constructions would be banned from areas immediately bordering the heritage sites and those in restricted areas further from the sites would be subject to height limits from three to 12 metres. Within the palace museum compound, constructions or trees that appeared at odds with the palace's ancient planning would be removed. But existing constructions outside the compound that exceed the height limits would be kept, according to the proposed plan. "I believe the best way to preserve heritage is to keep the structures, including the neighbourhood surrounding it, as they were in the past," Kong said. "That is to say, the courtyards surrounding the imperial palace should be kept and renovated when necessary. If we demolish them and build lawns or new buildings that do not exceed the height limit, we would also be ruining the heritage." The Palace Museum has also pledged to put together a list of its relics and antiques that are currently kept outside the museum, in order to bring them back to Beijing in the future, the Beijing Times reported. In 1933, the Kuomintang government transported most of the museum's collections from Beijing to Nanjing , Jiangsu province, following the Japanese invasion. About 600,000 pieces were later shipped to Taiwan while more than 100,000 pieces remained in museums in Nanjing.