Bomarsund ruins are the ruins of a fortress that was built by Russia in the 19th century on the island of Åland, which belonged to Russia at that time. The Bomarsund era ended abruptly when the fortress was destroyed by a British-French attack in 1854. This event also led to Åland becoming a demilitarized zone. The ruins of the fortress are today one of the most remarkable historical sites in Åland.

Today, visitors can explore the ruins, including some granite walls and four tower remnants, spread across an archaeological site covering 870 hectares. The area also features the new Bomarsund Visitor Centrum and Museum, which I totally recommend to visit before going to the ruins. The museum ticket price is approx 8 € from the adult.