The Örö fortress island has been a closed military area for a hundred years. It showcases the history of Finland's coastal defence, from the days of Tsarist Russia until the present day. The island's main sights include the well preserved barracks, heavy Obuhov guns, defence posts and fortifications from various eras. Thanks to its history as a closed fortress island, Örö has evolved into one of Southern Finland's key concentrations of threatened species and habitat types. The island is managed by Metsähallitus