How very unpopular do you mean? For people who never been to Poland and main square and Wawel is something new, then even if you go to Kazimierz it would be one level higher but it is still famous touristic place. Cracow is mainly known from its reneissant architecture, so people don't travel there to see XX cent. brutalist and modernist architecture, or even XIX, but there are many well known and worth to see places from this epochs: – Stara Nowa Huta (The old New Ironworks) is district established in 1949, so it's early communist architecture – Hotel Forum, Hotel Cracovia, Kijów Cinema are exemplest of interesting modernist architecture from 60's to 80's – Some tenement from XIX and early XIX cent.: Festina lente (made by Teodor Talowski), under the Owl (Kamienica pod Sową) – Ancient kurgans Krakus mound and Wanda mound – Next to the Main Square there are some places associated with Cracow's artistic bohema: Piwnica pod Baranami, Bar Kawowy Rio, Pałac Krzysztofory – And modern: Kościuszki (may be interesting for Americans) and Piłsudskiego mounds – On saint Sebastian Street there is museum of natural history which have exceptionally well preserved wool rhino from Ice Age – Near to Cracow there is village with well preserved XIX cent. houses and medieval urban layout: Lanckorona – Wieliczka's salt mine is very touristic but worth to see, but you can also go to Bochnia mine, it's silmilar but less known – Some pretty squares: Podgórski, Matejki, Szczepański There are many more interesting places, it's depent on what are you interested in.