Wunu Mountain, in Huanren County east of Benxi, is the site of the original capital of the Goguryeo kingdom — one of the Three Kingdoms of ancient Korea, which ruled this region from 37 BC to 668 AD. The mountain city ruins include defensive walls, gates, palace foundations, and residential structures dating back two thousand years, as well as earlier remains going back to the Neolithic period. The UNESCO World Heritage inscription in 2004 recognised the mountain city as part of the "Capital Cities and Tombs of the Ancient Koguryo Kingdom."
The site requires some effort to reach from Benxi — Huanren County is about 100 kilometres east — but the combination of historical significance, archaeological remains, and mountain scenery makes it worthwhile. The Huanren Reservoir nearby adds scenic interest to the journey, and the area has a pleasantly remote, unhurried character compared to the more touristy sites around Changbaishan.