Olavinlinna is a medieval castle located in Savonlinna, Finland. Built in the late 15th century, it was originally constructed to protect the region from invasions by the Swedes and Russians. The castle features impressive stone walls and towers, making it a significant historical landmark. Today, Olavinlinna is a popular tourist destination and hosts the annual Savonlinna Opera Festival. Visitors can explore its well-preserved interiors, learn about its history, and enjoy stunning views of the surrounding Saimaa lake. The castle's unique architecture and scenic location make it a must-see for anyone traveling to Finland.