The Suoyang City Ruins (锁阳城遗址) are the remains of a walled garrison city founded in 111 BC during the Han Dynasty, about 75 kilometres east of Guazhou. The earthen walls still stand up to 6 metres tall in sections and enclose an area of about 1.8 square kilometres, making it one of the better-preserved Han fortress complexes in Gansu. The Ta'er Temple (塔尔寺) inside the southern wall is a working Buddhist monastery with a Tang-era pagoda — the oldest standing structure in the area.
The site is inscribed as part of the UNESCO Silk Road World Heritage designation. The surrounding landscape is part of the Gobi — low dunes, dry salt flats, and the distant Mazong Mountains — and the ruins sit in it with an appropriate desolation. A small archaeological museum at the entrance displays pottery, coins, and wooden documents recovered from the site. Getting here requires a private vehicle or the tourist bus from Guazhou; combine it with a visit to the Yulin Caves for an efficient day in the area.