Visby is a great cute litle town. Lots to see and plenty of places to relax. I do recommend to visit during the yearly medieval week.
A feeling of traveling back in time for adults and great fun for kids.
Visby was a pleasant surprise for me. Visby gave me an insight of what Swedish life used to be like, culturally and religiously.
There were a lot of old churches and ruins that was rather intriguing. They do allow walk abouts within the compound but they close the area at 4pm. There are plenty of bars and a couple of clubs around Market Square if you are looking to grab a drink or two. There is also a supermarket by Market Square should you need anything. I would highly recommend that you head out towards the beach and just sit there and enjoy the sun and the view. If you could spare some time, having a picnic there would be awesome!