Suomenlinna is a sea fortress and UNESCO World Heritage site accessible by a short ferry ride from Helsinki. The fortress offers a glimpse into military architecture and Finnish history. While some areas are accessible, the uneven terrain and cobblestone streets can pose challenges for visitors with mobility issues. Exploring independently is common, allowing for flexibility, but guided tours provide deeper insights into the fortress's history. Seasonal restrictions are minimal, though some museums and services may have reduced hours in the off-season (October-April). A round-trip ferry ticket costs approximately 5 EUR, and entrance to the fortress is free, though some museums charge admission. A typical visit lasts 3-5 hours, allowing ample time to explore the various islands and historical sites.