Three Pools Mirroring the Moon. There are islands in the lake and there are lakes on the islands. On the south side of the largest of the three manmade islands in the Outer Lake, there are three hollow stone pagodas rising from the water, each with five openings. These stone towers were first built in Yuanyou in the fourth year of the Song Dynasty (1089). On a moonlit night, the pagodas are reflected on the water, producing the wonderful illusion of one moon in the sky having three reflections in the lake. At this time, local folk will put candles in the hollow tops of the pagodas.