Zhengding ancient city was once surrounded by two layers of walls – the inner and outer walls. While these have mostly been destroyed (most significantly during the Japanese occupation) some traces of the original structures do remain.
The north city gate stands right next to Hua'an East Road and used to be the entrance to the city (nowadays, the road dodges around the ruins). Unalike other sites, this is completely open to the public to poke around for free, although at the time of visiting (July 2017) there is some scaffolding and restoration work going on.
I loved being able to see the bare structure, with its loose bricks, dirt and all. While it took only a minute or two to have thoroughly inspected the gate, it was still worthwhile checking it out for the historic value. Although I'm not sure what their restoration work involves, hopefully the gate isn't being completely rebuilt, and there seemed to be some attempt at landscaping the surrounding dusty mud area which could make a lovely park in the future.