Kaifeng is ringed by a relatively intact, much-restored Qing dynasty wall, which you can climb up at various points. There's precious little to see from up top and it can be punishingly hot on a sunny day (bring plenty of water and a hat). In fact, the best way to appreciate the bastion is to walk alongside it at ground level, through various small parks and with plenty of local life to observe.
Today’s bastion was built on the foundations of the Song dynasty Inner Wall (内城, Nèichéng). Rising up outside was the mighty, now buried Outer Wall (外城, Wàichéng), a colossal construction containing 18 gates, which looped south of Po Pagoda.