Each year in Lhasa, the capital of China's Xizang Autonomous Region, the repainting of the Potala Palace becomes a citywide celebration. Residents lovingly refer to the palace's freshly whitewashed exterior as the "sweet wall," a nod to the centuries-old paint mixture made of white lime, milk, sugar, honey and locally grown saffron. More than just a way to preserve ancient architecture, it's a ritual steeped in tradition—and literal sweetness.