The Lakes (Søerne) in Copenhagen, Denmark, are a row of 5 rectangular lakes (the 2 closest to Vesterbro are, combined, approximately the same size as the other three) curving around the western margin of the City Centre, forming one of the oldest and most distinctive features of the city's topography. The paths around them are popular with strollers, bikers, and runners.
Originally the area, which the lakes now form, was one long stream. It had an arch shape and was just outside the city levees. In the early Middle Ages, a need of water for watermills was determined. As a result of this a dam was built and the Peblinge Sø was created.
As a result of a siege of Copenhagen in 1523, it was decided to expand the entrenchments in order to improve the fortifications of the city. The levee at Peblinge Sø was expanded and another was created, which resulted in the creation of Sortedams Sø. In the beginning of the 16th century, Sankt Jørgens Sø was created, by further damming. This made it possible to flood the banks and lakes in case of an attack.
Peblinge Sø and Sortedams Sø also served as reservoirs for the city. In the middle of the 18th century they were discontinued as a source of drinking water, due to poor water quality.
The first bridge, Fredensbro, was built across Sortedams Sø in 1878 as a small wooden bridge. The current Fredensbro is a wide levee, that separates the two basins. The vertical slopes of Peblinge Sø and Sortedams Sø were made in 1929, where the pathways surrounding the lakes also were made. In the 60's it was suggested a four lane city ring be constructed, but the project was disbanded and the lakes were granted the a status of a protected area in 1966.
Currently, the landmark consist of three artificial lakes, which are divided into five basins: Sankt Jørgens Sø (Saint George's Lake) is made of two basins (south and north); a single basin of Peblinge Sø (Student Lake; pebling means "little priest", and was used metaphorically for any student in the elementary and secondary schools in Denmark during the time when the church was the sole provider of education); Sortedams Sø (Black Pond Lake or Black Dam Lake) consists of two basins (north and south).
The lakes inlet is through piped streams, which jointly provide water from the wet-area Utterslev Mose, the lake Emdrup Sø and to a lesser degree the lake Damhussøen. From the lakes the water is streamed further on. The water has an average time in the lakes of approx. one year.
The water in Utterslev Mose and Emdrup Sø is very high in nutrients. As a result of this, large quantities of algae formed in the lakes and the water became rather unclear as well as hindering animal and plant life. In 1999 the municipality of Copenhagen erected a water treatment plant by Emdrup Sø, to clean the water that was being led to the lakes. This allowed for the re-creation of the water environment. Currently the water is much more clear and animal and plant life are present.
The lakes primarily serve as a recreational area and the paths surrounding them are popular for strolls and a favoured running route. The total distance around the lakes is 6.4 km.