Today I got a cool postcard from Finland! The postcard shows a view of Olavinlinna, a 15th century stone castle. Also called St. Olaf's Castle, it is the oldest surviving northernmost stone fortress. It is located in a strait in Savonlinna and has three towers. It hosts the Savonlinna Opera Festival. The postcard is an official Postcrossing card, FI-2336108. Thanks Mervi!