We are on the 10th August Ventura Cruise (with MiL and FiL) and I wondered if there was anything worth seeing within walking distance from the ship. Or is there a reliable bus that we could get to Porto ourselves? My relatives worry if we go too far from the ship and would prefer to be on an organised trip - but the cost of them is too expensive to do a trip in every port and we've all done the wine /river cruise/ site see trip in Porto before.TIA.