Great parts of Paris are really great, and only exist in Paris. No where else in the world has the same attractiveness or value. But, poor part is quite poor, and just like a normal city in Europe. Cleanliness of the city is somewhat disgusting. Such a contrast is sad. If i point out another issue, metro stations are hard to find. Places like London or Tokyo has large signs of metro stations, even if some people think it is not aesthetically good.
Insider Tip:Tourists with a big baggage cannot enter museums. Find a locker room at stations connecting to other cities, such as Gare du Nord, or Gare du Lyon. Nothing at Metro stations or neighbourhood around these famous museums except a few places.