Wikipedia
Sognsvann (or Sognsvannet) is a 3.3 km circumference lake just north of Oslo, Norway.
Lying just within the greenbelt around Oslo, the lake is a popular recreational area, used as a camping, picnicking and bathing destination for the residents of Oslo during the summer, as well as a cross-country skiing, skating and ice fishing destination in the winter. The trail around it is used for walking or jogging all year. Every year in August, swimming and running take part in Sognsvann as part of the Oslo Triathlon. Cycling around the lake is prohibited due to large number of people covering this road on foot. Disabled access is good to and around the lake.
Part of the lake's popularity stems from its easy access from Oslo; Sognsvann station, located on the south end of the lake, is the final stop on line 5 on the Oslo T-bane.
Svartkulp ("The black pool"), a small forest lake which is one of three nudist beaches in Oslo, lies a few hundred meters to the east of Sognsvann. The geographical center of Oslo municipality and county lies in the middle of this pool.
Sognsvann is a rapid transit station of the Oslo Metro's Sognsvann Line. It is situated Kringsjå neighborhood of the Oslo, Norway, borough of Nordre Aker. Located from Stortinget, the station is served by Line 5 of the metro every fifteen minutes. Travel time to Stortinget is sixteen minutes.
The station opened on 10 October 1934 at the same times as the rest of the Sognsvann Line. The station received a major upgrade in 1993, in which it received longer platforms. The new station was designed by Arne Henriksen. The station is located next to and serves the Norwegian School of Sport Sciences and the National Archives of Norway, as well as the recreational area around the lake of Sognsvann.