No trip to Porto is complete without doing a cruise along the Douro River. There are several choices of cruises, ranging from the 6 bridges cruise which lasts about an hour, up to ones that are full day excursions which require a train ride back to the city.
We felt that the 6 bridges cruise would more than suffice. After speaking with the concierge at the hotel, he informed us that for the most part doing anything longer than the 6 bridges cruise was not really worth the time. The next shortest cruise is about 6 hours long, unless you did a private river tour in which you could choose the length of the cruise you desire.
The 6 bridges tour heads towards the Atlantic Ocean, but once you get to the point where the river begins to widen.
Views of the city and port wineries are abundant from the cruise and is well worth your time.