This is almost the only place in Finland where a clear tidal phenomenon can be observed. Strömma is the narrowest strait between Kimitoön Island and the mainland. The old canal was built in the 1840s. In the 1890s, it was enlarged into a narrow open canal with a strong current.
To the west of the old canal, a new canal was built in the 1960s which is 28 meters wide and 5.5 meters deep. Across the canal a lift bridge was built operated by electrically driven mechanical machinery.
In the vicinity of the canal there is also a canal keeper’s house and Strömma pilot station. The pilot's hut in Strömma is the only pilot station in this area of the sea that is associated with a canal.
Some of the buildings that once belonged to old the canal community on the island, can still be found between the two canals.
On the south-eastern shore of the bay the out buildings of Strömma manor house can be found, surrounded by cultivated fields. The oldest parts of the main building originate from the 1830s.
History and transport needs.
In the 1820s, Robert Bremer, who owned the Tykö mill in Bjärnå, found a rich iron ore deposit in Vineme on the Kiskonjoki River. The excavated ore and limestone used in the processing had to be transported by road around Kimito, as Strömma was too shallow for the large barges.
The basis for the future of Strömma canal was the economic upswing during the 1820s and 1830s when extensive canal construction was planned in Finland. The largest project being the Saima canal, which commenced in the 1840s.
The dredging work for Strömma canal began in 1844 with the consent of Emperor Nikolaj I. A few years previously, the owner of the Tykö factory in Bjärnö, Robert Bremer, had begun to investigate the possibilities of renovating the straits at Strömma Kimito, but the work did not lead to any results. The new owner of Tykö factory, Viktor Zebor Bremer, offered, for a fee, to allow both a canal and a lift bridge to be built in the Kimito straits. According to the agreement, the owners of Tykö factory would maintain the area when the work was completed and, as compensation, they would charge a fee for any vessels using the canal. The canal acquired a pilot in 1852.
The width of the canal was initially less than ten meters and it was about three meters deep. The floating bridge was made from iron manufactured at Tykö factory in 1897. The canal keeper’s house was built in 1897 (B. Granholm). During the years 1896–1898, the canal was expanded and the road improved by a steel lift bridge across the canal; this was built according to drawings made by K. Lindberg. A new canal was built in 1967–68 to the west of the old canal.
In the 19th century, a small community developed around the canal with a school and a shop. The canal was an important hub for traffic and within its vicinity, Strömsholm’s sawmill was founded in 1875. There was also a small shipyard at this location in the 1870s and 1880s.
The estate of Strömma, was a tax-free farming model used to teach farming methods to local farmers; it was mentioned in written sources for the first time in 1434 and its owners have included the Fleming family, and the De la Gardie and Oxenstierna families. There have also been iron mines on the estate’s land. After the 1830s, the estate’s manor house was rebuilt in the 1850s, 1880s and 1930s.
During the 19th century, the canal was an important hub for traffic and a small community with a shipyard, sawmill, school and shop developed around the canal.
The swedish and finnish text borrowed from: http://www.kulturmiljo.fi/read/asp/rsv_kohde_det.aspx?KOHDE_ID=4152