Printing units comprising several printing groups, and printing tower

The invention relates to a printing unit (16; 17) comprising several printing groups (03; 04; 21; 22; 28; 29; 31; 32), each of which is provided with at least one plate cylinder (07) and at least one transfer cylinder (06) that is arranged so as to cooperate directly with the plate cylinder (07). The printing unit (16; 17), which is embodied as a nine-cylinder satellite printing unit (16; 17), is equipped with four plate cylinders (07) and a counterpressure cylinder (18) that is configured as a satellite cylinder (18). At least one inking roller of an inking group (09) is disposed so as to cooperate directly with the plate cylinder (07). One respective plate replacing mechanism (11; 11a; 11b), which encompasses a front section facing the associated plate cylinder (07), is assigned to at least two plate cylinders (07) that are placed next to each other in a horizontal direction.