It depends on the where the tour goes you will probably have several tours to choose from.
On the cruise we were on with Orient lines we had 17 different excursions for 2 days
Also depend on your stamina
You may want to check if others on your cruise are doing private tours ..less people about the same cost as ship's tours.
No waiting & wasting time for everyone to be back on the bus at each stop.
Alexandr Pushkin, Carnival-Holiday, HAL-(old)Westerdam, Orient lines-Marco Polo, Royal Olympic-Olympic, NCL-Dream, Dawn-Princess, ACCL-Grande Caribe, Oceania-Insignia (3), Regatta(4) Marina (1) St Lawrence Cruise Lines-Canadian Empress
Scenic River cruise June 11,2012