sorry, but as a polish person I can confirm that city of Katowice has around 300k population. The urban area around that city has 2.4 million, but it's not called Katowice, because it includes around 10 other cities and it's called Silesian Urban Area.
Same with Gdańsk. Gdańsk alone has fewer than 500k inhabitants. Only the area called the Tricity, including the cities of Gdynia and Sopot along with Gdańsk approaches 1 million.