Synninlukko refers to a fine gulley formation which is located between Jämsänkoski and Jämsä, only 7 kilometres (as the crow flies) from the centre of the town of Jämsä. Synninlukko is a shady, 50 metres wide gorge, bordered by craggy cliff walls. The territory is protected and contains rare flora. The wet swamp areas originate from several springs. During hot summer days, the air in the valley remains cool, as the sunlight cannot reach the bottom of the canyon. In spring, the rocky walls are decorated with an impressive ice covering.
There are several local folktales concerning Synninlukko. The dusky cliffs have provided a great hideout for generations. During the Russian wartime occupation at the beginning of the 18th century, the Great Wrath, as Finns call it, Synninlukko was used as a general hiding place for the local people. The location has also occasionally sheltered villains and vagabonds. At the bottom of the gulley, there is a spring which provided the refugees with drinking water. A story tells that the waterhole of Synninlukko is so deep that once when a calf fell off the cliff into the spring, its body was found in the Jämsänjoki River; or according to the wildest yarns: even in Lake Päijänne.
The end of the name 'lukko' (a lock or locket in modern Finnish) originated from the agent dialect of Häme, meaning a gully, bordered with cliff walls. The local people of Jämsä would have called such a formation a 'rotti'. In fact, the name Synninlukko is older than the modern Finnish word 'synti' (sin), which has mislead people into thinking of the sins of war or sinful people. Surprisingly, this agent word refers to birth, as 'synnyinlukko'; 'a gulley of birth'. Apparently, the gulley has been the birthplace of some unknown important person who has been escaping from some oppression.
The Synninlukko formation is quite easy to access. A road leads almost to the end and there is a lay-by for parking. The path measuring 1.8 kilometres to the destination is easy to walk, although, the path which leads up from the gulley is quite demanding.
Address: Synninlukontie 140, Jämsä
GPS: 61°52.9521', 25°06.6057'
Turn left from the Pääskysmäentie road after the cemetery of Miekkainpetäjä, onto the Haaralantie road. Drive straight ahead until you see the crossroads of Synninlukontie, where you turn left. In the fork of the road, stay on the left main road. After a kilometre, you will see a parking area on your right and a wooden sign displaying "Synninlukko".
The last forest road is not suitable for cars, but with a mountain bike you can drive up to the destination. Wooden signs lead to the designation. Occasionally, the private road may have poor winter maintenance.