Sooner or later these poor areas will improve and cities like £ódź seem better for the old buildings which very much form an architectural unity and give the city its unique atmosphere. Once they're gone, they're gone for good and replaced with the slums of tomorrow. Of course if there's no architectural merit at all and the residents' lives are made miserable by their surroundings it's a different story.
For one day only, the Warsaw Elizeum is open. If you're in town and haven't been before, it's very worth it. Normally, it's visiting only by special arrangement.
Demand is likely to be high, so turn up early.