Across from the Science Museum, was an even better museum of history. It starts at prehistoric times, all the way to current times, although by the time you get to China re-unification times, the version of history is a bit more "fluid".
They have a festival where people would climb a tower of buns that was designed to ward off bad spirits or bad luck:
The museum was quite well done, and definitely is worth 3-4H at least. Sadly the first time we only had 1h45 because we were told by someone in the Science Museum that 1h would do it. The only part that wasn't a bit weird was the reunification with china part, and how history got a bit fuzzy from that point on, which I guess is not that surprising...