Flying to Stockholm, then to Visby, then to Poland

Staying in Uppsala is not a bad idea. From the mainland you can reach Gotland by plane or by ferry, if you book in advance the ferry tickets can be very cheap, 95 kr if I'm not mistaken.

There are no ferries from Gotland to Poland, you can either take the ferry from Visby back to Nynäshamn and catch a ferry to Poland from there. Or, take the ferry from Visby to Oskarshamn, bus or train to Karlskrona (world heritage town) and a ferry to Poland from there. If you choose the latter route, you can include stops in Kalmar and some glass works in the area, and it is an area with some beautiful scenery.

Thank you so much for the info. Maybe I should start a different thread, but how many days would you recommend in Visby. We were thinking about 4 days, but is there enough to do there, or should we spend even more time if it is a good place to relax?

I love Gotland, so I might be a bit biased, but you easily spend a week on the island. Visby itself is a nice town. The medieval city centre and the 3.5 km long old city wall are both on the world heritage list. And the game of thrones-crew was there recently to scout filming locations… So for medieval and hanseatic architecture there is a lot to see.

You did not state when you are going, but summer is the time to visit Gotland. It is a popular holiday destination for locals (but as far as I can largely unknown to north americans). So many restaurants will be closed if you go in the winter. But in the summer you'll find Glassmagasinet in the harbour, they claim to be the largest ice cream bar in Sweden with 319 flavours. Ranging from common flavours like chocolate and raspberry to more unusual ones like tiramisu and aloe vera, to the truly bizarre like goats cheese and honey or baltic herring and chives. Make sure you also try the local dessert saffranspannkaka, sort of a baked rice pudding flavoured with saffron and almonds, served with whipped cream and dewberry jam.

Apart from Visby you can explore the rest of the island. It is easy to explore, bike, or bus/car for the more distant regions. Other sights are Fårö, north of mainland Gotland, where director Ingmar Bergman lived and is buried. Or you can just find accomodation close to the sea and spend some time relaxing. But as I said, it is popular in the summer so book somewhere to stay well in advance.

If you are visiting Stockholm I suggest you try the wonderful archipeago here. I also suggest you take a fast visit to Aaland. Youll get to Aaland for a couple of euros. Gotand is another of my favorite destinations. I suggest you go here early summer because the tourists are not occupying the whole island yet. Like May or June.
Visby got a lot of exciting buildings, museums, nice people, restaurants, cosy hotels and B&B:s. I went here in 2016 on a job and found a nice B&B called Tjarstugan(Tar cottage) close to the medeivel wall.
I show you some pictures on https://world-info.se/europe/northern-europe/scandinavia/sweden/europe/northern-europe/sweden/other-places-in-sweden/visby-gotland/

For a beatiful scandinavian experience I recommend you to go observe wildlife. Mooses are unique creatures and I was blown away how tall they are. It really was the highlight of our trip. Check their offer we were excited by the plan of the whole day. https://www.outdoorvisit.com/tour/16-stockholm-moose-wildlife-safari/

Thanks for the info on this tour. We really like being in the outdoors and finding interesting things to see in nature, so we will look into this!