Building work started Saturday to expand Tibet Museum in Lhasa, capital of Southwest China's Tibet autonomous region.

The project is set to be completed in 2020 and will expand the 23,000 square-meter building to 58,000 square meters at a cost of 660 million yuan (about 100 million US dollars).

The building will maintain a traditional Tibetan style, and will use solar energy, taking advantage of the city's abundant sunlight, according to Liu Yi, one of the museum designers.

After completion, the museum will be able to accomodate 7,000 visitors a day, according to the region's cultural relics bureau.

The museum has been closed since December 2016 to prepare for the expansion. During the construction, the museum will organize exhibition tours in the region.

A relic preservation center will be built for Tibet art treasures protection and study, and there will also be areas for public education and entertainment.

The Tibet Museum has about 520,000 pieces of collections, including thangka, Tibetan Buddhist paintings on cotton or silk applique, Buddhist statues and jade and porcelain containers.

There are also many priceless collections, such as a pottery cup made 4,000 to 5,300 years ago, a century-old Buddhism sutra written on birch bark, which is the only one of its kind in the world, as well as edicts on gold foil issued by the emperors of the Qing Dynasty (1644-1912).

It was opened to the public in 1999, in order to mark the 50th anniversary of the establishment of the People's Republic of China as well as the 40th anniversary of the democratic reform in Tibet. It is the first and largest museums in Tibet.

The museum has already shut down since December 2016, but during the years of renovation, its collections will continue to be exhibited through tour exhibitions in other museums out of Tibet.