Speaking about the thangka piece, Zhang Jie, curator of the exhibition, says: "It's like a comic book connecting many key events, and thus has huge significance as a historical reference."

However, Zhang says all important witnesses to history do not necessarily have to be artworks, and he recommends an epigraph carved on stone, which was unearthed in Beijing.

It records that Lun Boyan, a descendant of Lun Dongzan, once served as a border official for the Tang court.

During the Tang Dynasty, today's Beijing was a frontier area.

"The epigraph says that many other members from the family also defended the borders for the Tang court," says Zhang.

"The sons of a Tubo noble also worked for the Tang court. That clearly shows the close relationship between Tibet and inland areas at that time."

He also points to other exhibits that show such links.

He says a copper government seal from Lhasa during Mongol-led Yuan Dynasty (1271-1368) shows the rule of China's imperial government over Tibet.

And, a letter sent by the Tashi Lhunpo Monastery to Emperor Qianlong in the Qing Dynasty conveys the local people's gratitude for the imperial government's efforts in fighting foreign invaders.

Dwelling on the theme, Han says: "We (through the exhibition) want to show that the culture of the Tibetan ethnic group has a crucial place in Chinese culture as a whole.

"Tibetans play an important role as different ethnic groups form the Chinese people, which is unity in diversity."

Han expects the exhibition to help people better understand the importance of cultural diversity and to safeguard national unity.

Tibetan Buddhism is also a key theme at the exhibition which juxtaposes many sutras, Buddhist statues and other religious artworks.