Across the Douro River on the opposite side of Oporto is Vila Nova Da Gaia, where all the famous port wine cellars are located. The D. Luis I Bridge spans the river at the Cais da Ribeira. You can walk across the bridge and get to the Cais da Gaia, where there are several good restaurants.
I took the funicular on the Oporto side with my husband and ascended to the bridge. After walking across the bridge we reached the riverside and chose a restaurant. The food was traditional Portuguese fare served by friendly and professional staff. The meal was delicious and topped off, of course, with an espresso and a bit of port as we watched the night descend and all the lights of Oporto shine on the water.
An interesting story was told by the bartender, who showed us the lines, markings, and years on a post in the restaurant. These markings show the levels of water during times of flooding in the area. These floods are not all that uncommon for the riverbank. So we were told that the owners of the restaurants and shops just refurbish. Many of the restaurants have been there for years.