Rookery (slum)
A rookery was a colloquial term given in the 18th and 19th centuries to a city slum occupied by poor people and frequently also by criminals and prostitutes. Such areas were overcrowded, with low-quality housing and little or no sanitation. Poorly constructed dwellings, built with multiple stories and often crammed into any area of open ground, created densely populated areas of gloomy, narrow streets and alleyways.
Read more about Rookery (slum): Etymology, London Rookeries, Other Rookeries