In Rotterdam, everything is "near" thanks to the metro: if you arrive at the Cruise Terminal, you will have to take the subway at "Wilhelminaplein" (Line E) to "Beurs" and there you can either join "Blaak" by foot or with the other metrolines (A/B/C). Blaak is one of the hotspot for typical Rotterdam's architecture with the Markthal, the Cube Houses and the Rotterdam weekly market on Saturdays (one of the biggest in Holland) :) Just a one minute walk and you will discover the old Harbour (on the other side of the Cube Houses when you exit the metro station!) Hope it helps! ;)