sites between Copenhagen and Stockholm

How does this fit in with your overall travel plan and will you only have 3 days for this including time in Stockholm?
Also are you taking the train or renting a car?

I will be in Stockholm for 3 days. I have two extra days on either side of those 3. Sorry I wasn't more clear.

Thanks!

I'd say that Visby and Gotland is the obvious answer.

Thank you Badger!

I‘d say Visby is a nice choice, but maybe not the most obvious between Copenhagen and Stockholm, since it will require a couple of flights. especially the leg between Visby and Copenhagen can be expensive and might even require a change in Stockholm.
Other choices could be Eskjö or Kalmar.
Closer to Copenhagen you could visit Lund.

Thank you Morten. Taking trains though, so no flights.

It's not that hard to visit Visby between Stockholm and Copenhagen. From Stockholm take the ferry to Visby. When finished on the island, take the ferry to Oskarshamn, then a bus to Kalmar from where there are direct trains to Copenhagen. You can also stop by Glasriket on the way.

We are going by train from Copenhagen to Lund, renting a car and driving around Kivik, Ystad and staying the night near Ystad. Will drop the car back in Lund and take a fast train to Stockholm. Let me know if you need more info? We plan to stop along small places, farms on our way.
Nice read...
https://www.vogue.com/article/skane-county-scania-sweden-travel-guide

Thank you. I have heard from many sources that that is a beautiful area to explore.