The most prized lush herb-rich forest in the Helsinki Metropolitan Region

Horses of Russian Cossacks grazing in Helsinki in 1914, taking a break from working on the earthworks © Helsinki City Museum, Ivan Timiriasew
The horses of Russian Cossacks pictured above could very well be grazing on the construction site of the fortifications of Mustavuori, but this particular photo was taken somewhere else in Helsinki.

During the First World War, people and horses gathered to build earthworks in various locations on the fringes of Helsinki. One of the areas that underwent extensive construction was Mustavuori. The workforce consisted of both Chinese migrant workers as well as Finnish labourers.

At the top of the rock is the largest, 30-metre long cave, which in actual fact is a tunnel, with two mouths. On the western slope are two more caves hollowed out of the bedrock. Above these caves, on top of the mountain, a breathtakingly narrow gorge seven metres deep has been dug into the bedrock, with a width of only a little over a metre in places.

The structures are protected under the Antiquities Act, and Mustavuori is a nationally valuable built environment site. There have never been any permanent settlements on Mustavuori, but there was a hut village built by homeless people in the trenches until the start of the 21st century. There also used to be a limestone quarry on the eastern side of Mustavuori in the 18th century. The quarry pit in the south-east corner has been filled with water and turned into a pond.