Mingtan and Minghu reservoirs lie beside Highway 131 and are formed by dams located across the valley of the Shueili River to store water released from Sun Moon Lake for the generation of electricity. The Minghu Power Station was the first hydropower plant in Taiwan， and the Mingtan Power Station is the largest pumped-storage generating plant in Asia. The cycle of water release and pumping creates rare lake tides in Sun Moon Lake.【Old Tunnel and Viaduct】Two strongly alluring secret spots can be found in this area， one in the north of Checheng and the other beside the Mingtan Reservoir， namely， an old tunnel and viaduct. Everybody knows that Checheng is located at the end of the Jiji Branch Line， but during the Japanese occupation the railway continued upward to the Menpaitan Power Station (where the Daguan Power Stations are located today). The old tunnel is left from that railway line. It is 200 meters long， and was dug by hand in an S-shape along the slope. It is about 4.5 meters tall and five meters wide; the bottom half is made of stone and the upper part is made of fired brick， still standing strong after more than 80 years. This is a good place for visitors to get a taste of the mysterious past.The viaduct provides for a flow of water across the Dianzaikeng River. After the Japanese built the Menpaitan Power Station on the upper reaches of the Shueili River， they wanted to use the water left over from this power station to generate more electricity so they built another power station on the lower reaches of the river - today's Jyugong Power Plant. Between the two power plants， they built a water diversion channel of about five kilometers in length， which included a viaduct. This is an arched structure. On each side of the upper part of the diversion channel are five outlets that are opened to release water when the channel is full， creating ten beautiful waterfalls.