Vallisaari by boat – a former military island next to Suomenlinna

Vallisaari is Suomenlinna's neighbour on the other side of the Kustaanmiekka strait, and it has been part of the fortifications off Helsinki for centuries. Reliable records of the island's first fortifications date from the 17th century, and when Viapori was being built, a small fort, a redoubt, was built on the island. During the period of Russian rule, especially from the Crimean War onwards, batteries were built on Vallisaari and Kuninkaansaari. The island's best-known sight is the Aleksanterinpatteri battery, built after the Crimean War, which has a viewing platform on its roof.

People lived on the island until 1996, and at its busiest, in the 1950s, it had more than 300 residents. In 1937, a devastating explosives accident took place in the middle of the island, in the so-called Valley of Death. In 2008, the Finnish Defence Forces announced that they would give up the islands, Metsähallitus began preparing to open them in 2013, and the islands were opened to visitors in 2016.

Long military use has kept the ramparts and the meadows on the fortifications open and the island's nature exceptionally diverse. More than 400 plant species grow on Vallisaari, and it proved to have the richest flora of the more than 200 islands surveyed in Helsinki. More than a thousand butterfly and moth species are known from the island, and the old fortifications, caves and buildings are breeding and hibernation sites for five protected bat species.

From Vallisaari, a stone causeway leads to Kuninkaansaari. There are two marked loops: the 2.8-kilometre Aleksanterin kierros loop on Vallisaari and the 1.4-kilometre Kuninkaansaari loop, which runs across Kuninkaansaari to a sandy cove on the east shore and back.

The trip suits people interested in nature and military history, and anyone who wants to spend a few hours walking in peaceful archipelago nature right off the city.

In places, the paths run close to old fortifications and steep drops, so keep children close to you and stay on the marked routes.

The guest harbour charges a harbour fee for day visits too. You can pay online or at the harbour café The Pier and the ice cream café Paja during their opening hours. Check the up-to-date prices and instructions on the guest harbour's website.

In the summer season, the island has several cafés, such as the harbour café The Pier on the Torpedolahti harbour square and the ice cream café Paja. The islands also have drinking water points, toilets near Luotsipiha and Torpedolahti, and several dry toilets. Check the cafés' opening hours before you set off.

Keep to the marked routes. Off the routes there are dangerous structures, steep drops and places at risk of collapse, and there may still be explosives in the ground left over from the 1937 accident and military activity. Swimming is prohibited in three places: in the Torpedolahti harbour area because of the busy boat traffic, on the shore rocks of the Kustaanmiekka strait because of the waves raised by ships, and in the Vallisaari pond.

Making fires, including the use of disposable barbecues, is completely prohibited on Vallisaari and Kuninkaansaari, and camping is not allowed on the islands. Dogs and other pets are welcome when kept on a lead, and their droppings must be picked up.