Vanhankaupunginkoski is culturally and historically significant area in Helsinki. The City of Helsinki was originally founded here by the rapids in 1550. The rapids are 200 meters long and have a drop of six meters. They are divided to eastern and western branches, between which there is an island. On the island operates the Museum of Technology. The western branch of the rapids is dammed. The dam is protected. There is a hydroelectric power plant connected to the dam. It is the oldest hydroelectric power plant still in use in Helsinki. During the summertime it is open to museum guests. The Power Station Museum operates in conjunction with the Museum of Technology.The whole area is now-a-days a popular recreation area.