The most strategic island...

in the Baltic Sea surely must be Bornholm.  The island is the site of this morning's objective, Hammershus, the largest medieval castle ruins in Northern Europe. The massive brick castle was built from the 1200s onwards, and is located on an imposing granite outcrop overlooking the sea (click to enlarge):

The huge brick tower and facade were expanded by the Lübecker’s of Germany in the 16th century, clearly seen in this image:

Our next call was to Østerlars Church, the largest and most famous of the four round churches on the island, dating from the 12th century. The thick–walled, white-washed drum was shining brightly during our visit:

After lunch, we boarded Zodiacs and bounced our way back to the Odyssey for a short dash to a nearby island group for afternoon activities: