The most popular city by population is Warszawa (Warsaw). The next largest cities by population are Krakow and Lodz, however, there is a large immigrant population in the small city of Wroclaw due to the presence of several large international companies – including IBM.
The population of Warsaw during the last century has increased 2.5 times, while the population of Krakow has increased 5 times during the same period. Krakow has a rich heritage and is the second most popular city among tourists and immigrants. http://www.immigration-residency.eu/immigration-to/poland/