To be honest it was purely by chance that I went to Vadstena. I was looking at a map of Sweden and said to myself that that lake looked interesting and saw it was called Vadstena. I didn't really know what to expect when I arrived but I wasn't disappointed!
The medieval style castle surrounded by a moat is imposing. It doesn't cost anything to go inside and there is lots of information about it.
You should also visit the Abbey. With a bit of luck you will find the choir rehearsing for you alone: a fantastic atmosphere! Sitting at the back of the church, listening to the crystal clear voices of the singers illuminated by candles is a timeless experience.
And finally, if you are in Vadstena for a day (or an evening!) in winter, then go to shores of Lake Vattërn. If you are lucky enough to arrive when the sun is going down, then you can sit on one of the little benches opposite it and enjoy the magnificent sight of the sun going down over the frozen lake.
Perhaps it was because it was winter and everything was covered in snow, perhaps it was because of that little walk to the lake while the sun was going down, or perhaps it was the singing of the choir in the Abbey, but one thing is certain, Vadstena has a magical atmospere! A small town with few things to visit, it nonetheless remains one of my best memories of my trip to Sweden, so I can only recommend you try it!