The ruins of Linhuan ancient city in Duji District preserve the earthwork remnants of one of the Tang dynasty's significant regional capitals — a city that served as a major node on the Grand Canal network before being abandoned as the canal routes shifted and silted. The perimeter walls, now reduced to earthen platforms several meters high in places, still outline the city's original extent, and the foundation platforms of major buildings are visible under the current farmland.
This is a site for archaeological imagination more than spectacular preservation — the landscape is flat and agricultural, and what remains requires some knowledge of the period to appreciate. But the scale of what's there is genuinely impressive, and the interpretive signs (in Chinese) give enough context to make sense of the earthworks. The best time to visit is late afternoon when low light defines the terrain more clearly.