Tibetplateau.org
Explaining brief history of Lhasa Shutun(Yogurt festival).
The 30th day of the sixth lunar month is celebrated with the hanging of a huge Thangka morning at Drepung monastery and afternoon at Sera monastery once in a year since time of the HH the 5th Dalai Lama in 17 century.Rest of 5 days, all local people and tourists go to the Norbulingka to watch Opera dances and for picnic.
The Opera dance was an ancient Tibetan traditional dance which found by the Master Thang Tong Gyalpo in 15 century.Even Shutun(Yogurt festival) is the most popularly summer festival of Lhasa.