Qiandao Lake is not a natural lake and it is not old. It is a reservoir, fifty-odd years on the map, created when a dam was put across the Xin'an River and the hills behind it became islands — 1,078 of them at the current count. The county town of Chun'an moved in 1959 when the water rose, and two older cities, He Cheng and Shicheng, went under with their eight gate towers and eighteen centuries of history still standing on the bottom.
What it became instead is the cleanest large body of water in the country. That is not a boast — it is the reason a bottled-water company built its brand on it. The lake sits on the Hangzhou–Qiandao Lake–Huangshan corridor, 129 km from Hangzhou and about 150 from Huangshan, and it works either as a two-day stop of its own or as the middle of that route.
The islands themselves are a mixed bag and it is worth being honest about it: most of the developed ones carry recent attractions — snake islands, monkey islands, lock islands, a floating bridge with a hundred-pound carp under it. The reason to come is not any single island. It is being on the water among a thousand of them, and then eating.
Two days is the right shape. One day on the boats through the central or southeast zone, one day for the edges — the forest oxygen bar, Qiuchuan village with its seventy per cent Ming and Qing Huizhou houses, a raft run if it is summer, or the 185 km cycle loop if you ride. Come in autumn for clarity, or in winter for empty water at winter prices.