'Letter to Boyuan' by Wang Xun.  [Photo/CCTV.com]

The rarity of the items now brought out of the Palace Museum's vast collection reflects the importance of this anniversary.

Meanwhile, the Palace Museum will open five more areas to tourists in October, including the Yanchi Tower with an exhibition related to emperors' birthday celebrations.

One of the most famous items is a 44-meter-long painting celebrating the birthday of Qing Dynasty Emperor Kangxi.

Founded in 1925, the Palace Museum is the largest museum housing ancient Chinese culture and art, with over one million items. The 90th-Anniversary exhibition runs for two months.