All cities were surrounded by walls during the good old (or bad old, depending) days in China. Nearly all are gone now. Ganzhou has an long section intact. I suspect it has been heavily restored. Some bricks are new, while others probably date back a long way, perhaps to the Song dynasty. Many have characters stamped on the bricks, but alas they apparently do not indicate date. The river on one side, the long winding wall on the other - in a park setting. Mainly locals, and not crowded. Quite nice.