Train from Stockholm on June 25,
Stay on June 25, 26,
Train to Copenhagen on June 27.
Lövmarknaden ('Leaf Market' - happens on midsummer's eve june 21 - in the town square, which is the 2nd biggest in europe after Moscow's Red Square)
http://www.karlskrona.se/sv/VisitKarlskrona/Sok-i-Destinator/lovmarknaden/
Floating sauna - expensive but awesome:
http://www.karlskronabastuflotte.se/
And ice cream - not particularly good, but outrageously massive.
http://stringofpearls.blogg.se/images/2009/p6240061_45023116.jpg
http://www.youtube.com/watch?v=0-NXp22aUIs&feature=youtube_gdata_player