Das ist das Herzstück von Porto.

Porto's riverside quarter, known as the Ribeira, is one of the city's oldest neighbourhoods and certainly one of its highlights.
The waterfront (Cais da Ribeira) is long strip of cafes, restaurants and shops overlooking the river and the Port houses of Vila Nova de Gaia on the opposite bank.

This is mainly a photo opportunity, and I wouldn't recommend any of the restaurants on the square. If you want to avoid the satellite dishes on your picture of the amazing colours on the tiled buildings, try taking your picture from up-hill, looking down to the river. The dishes face away from you and blend in better.

I guess this is a "must-do" place for Porto - it does have a lovely view of Gaia, and of the 2 nearby bridges (Ponte Luiz, Ponte Infantile). Lots of people around, buskers, restaurants, so great place to sit and people watch, have a drink, have dinner with a view.

I came at sunset, so the sun reflecting off the river, and off the buildings in Gaia was pretty. So why 3 stars? At the end of the day, it's "average" like most boardwalks, with the usual crowds, etc. I would not say it is extraordinary.

For a good exercise to go back up to the city, instead of taking the funicular, take the Escada dos Guinos, a set of stairs near the funicular, on the non touristic side of the Riberia. Of course you could walk down, but what fun is that - walk up the steps from the river level to the city level where the upper bridge of Ponte Luiz enters the city - quite a climb but the steps goes through a typical neighbourhood with beautiful view of the bridge and of Gaia as you ascend.

Another tip, walk the Ponte Luiz at sunset/dusk as the lights turn on - the view from the upper bridge of the city, of Gaia, of Mirador Pillar, of Riberia below, and the river at dusk when the water turns deep blue and the skies orange from the sunset - beautiful pictures to be had! (but probably over 2 separate days since it is quite a chore and takes time to get from River level to upper bridge level)