Despite the amazing and even terrifying continuity of Chinese culture, it is really astonishing how little of ancient China there remains for anybody to look at. Lewis off-handedly mentions at one point that there remains not a single surviving house or palace from Han China. There are not even ruins.It must be interjected here that a certain Wall does leap to mind, but beyond that, can you name another monument? This absence is indeed striking, and once stated seems like it should always have been obvious. Why? Are people's identities wrapped in culture but not at all with specific government administrations, therefore obviating nostalgia? ("We're in China, regardless of whether our own Parthenon still is.") Or for the conspiracy-minded, might it result from a pragmatic policy that each conqueror or dynasty has made sure to erase the monuments of preceding rulers, so they could create the past at their leisure, as Orwell suggested an ideal dictator would? Maybe it's something far more mundane; reliance on wooden structures that unlike the Coliseum or the Pyramids, don't weather so well?
There's no equivalent of the Parthenon or the Roman Forum, no Pantheon or Colosseum. You can come closer to the present: There's no real Chinese equivalent for Notre Dame or the Palazzo Vecchio. For all its overpowering continuity, China does not preserve physical remains of the past.
Finally, maybe a millennia-old strong central government of a large nation has left no room for the provinces to leave behind their own castles? Japan has a rich heritage of castles and kofun, but Japan was also not strongly unified until the seventeeth century.