Hello Ania Marysia. You asked an interesting question and I thank you for it. Not really "kamienica" and "dom miejski" have the same meaning in Polish.English proposes one word "townhouse" and Polish has two meanings connected with this word. "Dom miejski" can be a place of cultural meetings, different kinds of activities, it is a place of performances and town celebrations. "Kamienica" is usually a residential building, with several floors with an old-fashioned façade, in which there are flats with quite large areas and ceiling heights, with beautiful decorated balconies. Usually "kamienica" are located near the oldest part of the city. English proposes one word "townhouse" and Polish has two meanings connected with this word. "Dom miejski" can be a place of cultural meetings, different kinds of activities, it is a place of performances and town celebrations. "Kamienica" is usually a residential building, with several floors with an old-fashioned façade, in which there are flats with quite large areas and ceiling heights, with beautiful decorated balconies.Usually the tenement house is located near the oldest part of the city.
I hope I have answered your question.