Especially for my weekend city trips the most affordable accommodation were hostels. In general I prefer new stylish design hostels with a broad range of facilities. Hope you find some inspiration for your next city trip in one of the European metropolises: (Please click at the country to get to the list)

• Germany: Berlin, Frankfurt, Hamburg, Munich, Nuremberg
• Other Europe: Tallinn, Helsinki, Paris, Athens, Milan, Lisbon, Barcelona, Basel, London

–> maybe you are also interested in Hosteltipps in Asia or America