Hunt the Valley of Death on Vallisaari

Vallisaari was sealed from the public for over 200 years — a military fortress island where a catastrophic 1906 ammunition explosion killed dozens and left a scar called the Valley of Death. Alexander II's granite road still runs through the forest. Bat tunnels pierce the fortifications. In summer, over 1,000 butterfly species colonize the wildflower meadows that grew where soldiers once drilled. The military left; nature reclaimed.

What to do there

4 things to do

1. 1 Find the Valley of Death Explosion Crater History · Free

   From the Vallisaari ferry dock, follow the main path inland for about 10 minutes. Look for signs pointing to the 'Valley of Death' (Kuolemanlaakso). In 1906, a catastrophic ammunition explosion in the Russian military magazine killed dozens of soldiers and left a massive crater that split the island's landscape. The depression is still visible — a scar of raw rock and scrub vegetation where the forest hasn't fully recovered in 120 years. Stand at the rim and look down. The scale tells you this wasn't a small accident.

   Backup: If signage is unclear, follow the main trail towards the island's centre. The crater is the largest depression on the island — impossible to miss if you stay on the central path.

   Log Memory
2. 2 Walk Alexander II's Granite Road History · Free

   The military road running through Vallisaari was built during Tsar Alexander II's reign (1855-1881) — the same emperor who gave Finland its own parliament. The granite paving stones are original, laid by Russian military engineers to connect the island's fortifications. Walk the road from the ferry dock towards the southern battery positions. Feel the stones under your feet — they're rougher than Helsinki's city cobblestones, designed for military boots and cannon carriages, not civilian shoes. Count the granite blocks per metre — the uniformity tells you this was engineered, not improvised.

   Backup: The road is the widest path on the island. If you're on smooth gravel, you've left the historic route.

   Log Memory
3. 3 Hunt for Bat Tunnels in the Fortifications Adventure · Free · Optional

   Vallisaari's Russian-era fortification tunnels are now home to bat colonies — several species hibernate here in winter and roost in summer. The tunnel entrances are visible along the southern and eastern fortification walls, built into the granite. Some are gated (for bat protection), but you can peer through the bars. Look for dark openings in the rock face as you walk the fortification perimeter. The tunnels were ammunition stores; now they're bat maternity wards. Bring a phone light to spot the hanging forms if you visit late afternoon.

   Backup: Even if bats aren't visible, the tunnel architecture itself is worth finding — the brick-lined entrances with Russian-era stonework are photogenic.

   Log Memory
4. 4 Count Butterfly Species in the Wildflower Meadows Adventure · Free · Optional

   Vallisaari hosts over 1,000 butterfly and moth species — a biodiversity record for any Helsinki island, the result of 200 years without public access or development. The wildflower meadows on the island's western slopes (between the fortress walls and the shore) are the prime habitat. Visit between June and August for peak butterfly season. Walk slowly through the meadow areas and count distinct species — even non-experts can typically spot 5-10 different types in 20 minutes. The military left; nature took over with a vengeance.

   Backup: If butterflies aren't active (cloudy days, early morning), the wildflowers themselves are spectacular. Look for Finnish wild orchids in June-July.

   Log Memory