Tonghai County occupies the fertile valley of Qilu Lake. Mountain ranges surround the valley from all directions, separating it from Jingchuan in the north, Huanning in the east, Jianshui in the south, and Eshan in the west.
The county seat, which does not seem to have a commonly used proper name of its own (other than the official desination "Xiushan Subdistrict" 秀山街道) is located south of the lake, at the border of the plain and the mountains, separated from the lake by a mile-wide strip of farmland. The lake is surrounded by dikes, for flood control. The dike on the southern shore of the lake (the one facing the town) has a pleasant promenade on it; it is connected with the city by numerous concrete roads.
Tonghai's ethnic composition must have been greatly influenced by the Mongol conquest in the 13th century. To this day, the county has a large Muslim (Hui) population; numerous Hui towns and villages can be recognized from far away, by the domes and minarets of their mosques. The county also has Yunnan's only Mongol ethnic township (Xingmeng).
Tonghai is served by the new standard-gauge Kunming-Hekou railway. Several trains a day in each direction stop at 1 Tonghai Railway Station, which is located a few kilometers west of the county seat, near the road to Hexi Town. Similarly to other stations along the Kunming-Hekou Railways, the ticket office at the Tonghai train station has a complicated schedule (basically, it's only open around the times when a train passes through). There is also a train ticket office downtown, with a more sensible schedule.
- 1 Jukui Pavilion (聚奎阁). The symbolic center of Tonghai's old downtown (now, the town's tourist / shopping district).
- 2 Xingmeng Mongol Ethnic Township (兴蒙蒙古族乡 Xingmeng Mengguzu Xiang) (On Hwy S319 (S304), a few km west of the county seat). The only ethnic Mongol township in Yunnan. Although the people known as "Yunnan Mongol", or Khatso, trace their ancestry to the Mongols of Khublai Khan, who conquered Yunnan in the 13th century, they actually speak the region's indigenous Yi language, rather than Mongol.
- 3 Da Hui Village (大回村 Da Hui Cun) (Off Hwy S319 (S304), on the west side of the county). Decorated with Arabic inscriptions, Da Hui Cun and Xiao Hui Cun (the Greater Hui Village and the Lesser Hui Village, respectively), are known for their ornate mosques
- 4 Najiaying Mosque (纳家营清真寺 (Nàjiāyíng Qīngzhēnsì)). A large mosque in Nagu Town, northwest of Tonghai Lake
- Ride a bicycle (if you have one) around Qilu Lake. Besides the promenade along the lake's southern side, and paved dikes along irrigation canals, a network of paved roads crosses the farmlands that surround the lake.
- 1 Qutuo Pass Village (曲陀关村). Qutuo is the first village in Tonghai County as you enter the county from the west on Yunnan Hwy 319 (former S304), over the Qutuo Pass. As seen from the road, it mostly consists of shops selling the region's local products, of which the most famous is, apparently, is something called "Red sweet liquor" (红甜白酒 hong tian bai jiu). The other famous local product - seen at numerous roadside vendors - are white radishes, which grow to a remarkable size.