Imatrankoski in Imatra, Finland
Rushing through a shallow Finnish hollow the Imatrankoski rapids have been a popular tourist attraction for about as long as they have been known, but today, thanks to a massive power plant dam, the rapids are only unleashed according to a show schedule.
Formed over 5,000 years ago when ancient lake waters reshaped the landscape, the rapids are arguably the largest such feature in the country. Given their violent grandeur, it is little surprise that they quickly began attracting attention. As early as the late 1700s the rapids were luring vacationers and gawking naturalists in equal number. As the number of visitors to the raging waters grew, a cable car was installed that would ferry people over the deadly torrent in a bit of thrilling novelty. Hotels and other indicators of a burgeoning tourist economy also began to appear in the vicinity.
As opposed to doubling down on the attractions at the site, a massive hydroelectric dam was built across the river in the 20th century. After massive flooding caused by the rapids effected the surrounding communities, the dam was put up to staunch the flow of the waters. Today the former rapids are often just a dry riverbed. However during the summer months, the dam is opened a few times a day, unleashing the furious rapids once again to the delight of onlookers.
Even with this industrial innovation, the appeal of this natural wonder does not seem to have abated, and the rapids continue to draw huge crowds of visitors each year.