Suomenlinna Fortress is a UNESCO World Heritage Site located on a group of islands off the coast of Helsinki, Finland. Built in the 18th century, it was originally constructed by the Swedes to protect against Russian expansion. The fortress features impressive walls, bastions, and historical buildings, making it a significant military structure. Today, Suomenlinna serves as a popular tourist destination, attracting visitors with its scenic views and rich history. The islands are home to museums, cafes, and parks, providing a unique blend of culture and nature. It is accessible by ferry, making it an easy day trip from the city.