Located 25km west of Qinghai Lake past Heimahe, this salt lake is a popular side trip for a stunning optical illusion that occurs between noon and 4pm daily where, on a clear day, you can capture amazing photographs of skies and people mirrored onto the lake's surface. In order to get the best portraits on the lake, wear something bright (yellow, blue and red are great). Black and grey are hipster cool but they don't show up very well in images.
The K6961, a daily train (hard seat/hard sleeper ¥62.50/155.50, four hours, 8.25am) from Xining to Chaka (茶卡站, Chákǎ Zhàn) drops you just at the tourist entrance of the lake, a short distance from the lake itself. The train returns at 4.30pm so you could do the salt lake as a long day trip if you aren't coming from the main lake. A daily bus departs the main bus station in Xining at 10am (one way/return ¥100/240, five hours) and drops you at Chaka town, 2km from the lake, where waiting taxis will take you the rest of the way for ¥30; the bus returns later in the afternoon.
From Heimahe, you can flag down a bus to Chaka (roughly noon and 1.25pm) or hire a private car (¥320 return).