Parts of a medieval castle's walls have become "damaged" and "unstable" following recent bad weather, a council has warned.

Still standing after nearly 550 years, Olavinlinna or St. Olaf's Castle, is the northernmost medieval stone fortress in the world, lying about 220 miles from Helsinki. As the origin of uncountable ...

PETER GINN: Castles dominated the landscape of the medieval age ... so it can keep the blacksmiths going. Almost everything we need to build a castle is just a stone's throw away.

NARRATOR: Rooms in castles didn't have bare stone walls like the ruins we see today. They were covered with a layer of mortar, the medieval equivalent of plaster.Next, they were given a coat of ...