This is a Polish port, but there is not much to see in Gdansk. Should take a bus tour as we did, otherwise you will miss all of what you can see there, which is not much. we were shown Lech Walesa's home on the outside.
Tallin is the lovelist of ports, they are quite prepared for tourists and it is a lovely place to visit. We enjoyed all of it, we took a local tour bus and then went to the center of town. Very nice.
Wonderful port of call. Take all the tours you can, but the one which is stellar is the evening tour of the Hermitage, we really enjoyed this. There is so much to see, two days is not enough.
Riga is very pretty, although not as prepared for tourists as Tallin. However, some in our group liked it even more than Tallin, so it is a question of preference. Would have liked to see it more in depth.