Farmers sing during a ceremony marking the start of spring farming in Doilungdeqen district of Lhasa, southwest China's Xizang Autonomous Region, March 16, 2024.LHASA, April 7 (Xinhua) -- In Lhasa, the capital of southwest China's Xizang Autonomous Region, a remarkable event unfolded at the Dakpo astronomical observatory -- a structure with a history of over 300 years.