Isterinkoski

Isterinkoski is a rapid in the Muhos municipality. It flows in the Poikajoki River, in Poikajokilaakso valley. It has two main falls and rapids surrounding them. The total length of the rapid is over half a kilometre, and it has a total drop height of about 23 metres.

The rapid is located at the eastern part of a rift known as Muhosmuodostuma, extending all the way from Muhos to Hailuoto municipality. The rift was formed 1.3 billion years ago, when the bedrock in the area sank. The rift was only discovered in 1938 when the harnessing of the Oulujoki River was planned. The exact origin of the name Isterinkoski is not known, but the scholar Martti Haavio has suggested it has something to do with the legend of St. Gregory from the Catholic period. It may be that the spelling of the name (St. Georgio and St. Gorgi) has taken the form “Isteri” in Finnish.

Out of the two falls in Isterinkoski, the upper one is rather a sloping rapid (“slide”) than an actual waterfall. The lower one, however, is a reasonably steep fall, where the water drops more than 3 metres within a short distance. Both of the falls are easy to access because the paths are in good condition. The nature in the area is also well worth seeing, for the Poikajokilaakso valley is part of a national Herb-rich Forest Reserve programme. The vegetation in the area is exceptionally rich and contains several rare species (such as saxifrage).

Since Isterinkoski is a local attraction, there is good signposting and it’s easy to find. Cars can be left on a nearby parking area, where you can also find a fireplace. As a waterfall, Isterinkoski doesn’t rank at the top in Finland, because both the drop height and steepness in the two falls are quite modest compared to others. As a whole, however, the rapid is a beautiful and impressive place to visit.