Skjærsjøen

Marka is the name of the forested and hilly areas surrounding Oslo, Norway. It includes areas within the municipality of Oslo, but also large areas in Hole, Ringerike, Jevnaker, Lunner, Nittedal, Bærum, Asker, and other municipalities in Viken county. The name is actually just the finite form of mark (Norse mǫrk f) 'woodland, forest'. (See also Finnmark, Hedmark, Telemark, Marker and Aremark.)Though not designated a borough of Oslo, it is a major recreational area for the population of Oslo, and development in the area is for the most part prohibited. Despite being used frequently by many inhabitants of Oslo, especially at weekends, the fauna of marka includes species such as lynx, wolf, beaver, moose and roe deer. The term Oslomarka is usually used for all the recreational areas around Oslo. Marka is the administrative name for the part of it that lies inside the city limits. Neighboring municipalities (most of which lie in Viken) do not have the same kind of administrative division as Oslo, and thus do not have any separate administrative arrangement for their parts of the area. The area within Oslo municipality is divided into two parts. The population and agricultural areas of Marka are located mainly in two valleys, Sørkedalen and Maridalen. Oslomarka is further divided into: Kjekstadmarka Vestmarka Krokskogen Bærumsmarka Nordmarka Romeriksåsen Lillomarka Gjelleråsen Østmarka SørmarkaOf these, Vestmarka, Kjekstadmarka, Romeriksåsene, Follomarka and Sørmarka lie almost entirely outside the city limits.

Vettakollen is a hill and neighbourhood in the borough of Vestre Aker in Oslo, Norway. The hill lies west of Sognsvann and southeast of Voksenåsen and Holmenkollen, and measures 419 metres above mean sea level. The estimated population in the Vettakollen area is 7 600 people. The built-up residential area south of the hill is served by the Oslo Metro station Vettakollen, Gulleråsen, Gråkammen and Skådalen.The name stems from the beacon hill's former use as the site of a beacon (Norwegian: varde). Before modern times, such beacons were set alight on a series of hills to constitute an alarm system. The naming is found in other hills, such as Vardåsen, Varingskollen and probably Brannfjell.

Hammeren Hydroelectric Power Station (Norwegian: Hammeren kraftstasjon) is a hydroelectric power station located in Oslo, Norway. It is the only power station in Oslo, and among the oldest power stations still running in Norway. It has a total installed capacity of 5 MWp, and an annual production of 16 GWh. The power station utilises the waterfalls from Skjærsjøen to Maridalsvannet, with a total height of 105 m. It was established in 1900 by the company Christiania Elektricitetsværk, originally with four generator units, and increased to six units in 1901. In 1927, the six generators were replaced by a single 5.6 MW unit.

Tryvann is a small lake in Nordmarka, the forest area just north of Oslo city, near the Holmenkollen ski jump. By the water lies a cabin called Tryvannstua, in which there is a café open regularly during both summer and winter. On a hill above the lake looms the television tower Tryvannstårnet ("The Tryvann tower"), visible from most of Oslo. Tryvann is the entry and beginning of Nordmarka. It is used all year around. The key purposes of this area in the winter are skiing and cross-country skiing, whereas in the summer it is more commonly used for walks in the forest and biking. When referring to Tryvann, it is mostly referred to as the Tryvann vinterpark.

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 on the footpath around the lake is prohibited; however there is a dedicated cycling trail. 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 Metro. 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.Nedre Blanksjø ("The lower shining lake") is an even smaller lake a few hundred meters to the north of Svartkulp. A pyramid marking the geographical center of Oslo municipality and county is installed on the east side of it, alongside Ankerveien.

The Oslo Winter Park at Tryvann (Norwegian: Oslo Vinterpark) is a ski resort in Oslo, Norway. It is the most used ski resort of Norway. In the 1930s, the ski slope Tryvannskleiva was constructed, and the first race was held in 1933. The ski slope was later expanded with Tommkleiva, Wyllerløypa and finally with Tryvann Ski Resort. As of winter of 2010, the resort has 14 slopes and 7 lifts. There is only 1.2 km (0.75 mi) walking or bus distance from the Voksenkollen metro station.

Tryvannshøyden, Tryvannshøgda or Tryvasshøgda is a hill in Oslo, Norway, peaking 529 metres above mean sea level. It is named after the nearby lake Tryvann. It is known as transmitter site consisting of Tryvannstårnet and a guyed TV mast. From 1934 to 1966 the hill featured a speed skating venue, Tryvand stadion.

Frognerseteren is the end station of the Holmenkollen Line of the Oslo Metro, located in the Marka section of Oslo, the capital city of Norway. It the northernmost station in Oslo Metro, and is the station after Voksenkollen. The line to Frognerseteren was completed on 16 May 1916. The station has two platforms which, like other stations on the Holmenkollen Line, only accommodate two-car trains. The elevation of the station is 469 meters (1,539 ft) above sea level, the highest of all the stations in Oslo. The elevation difference between this station and the lowest in Oslo Metro (Stortinget), 478 meters (1,568 ft), is the highest elevation difference within a metro network in the world. The area around Frognerseteren has very little population, but is popular for recreation, with a restaurant and hiking trails or, during the winter, skiing. Tryvannstårnet is also within walking distance although Voksenkollen station is slightly closer.

Tryvannstårnet is a 118-metre (387 feet) tall broadcasting tower near Oslo, located 529 metres (1,736 feet) above mean sea level on the summit of Tryvannshøyden hill overlooking lake Tryvann. Tryvannstårnet was built in 1962 and has an observation deck at a height of 60 metres (197 feet), from which, weather conditions permitting, the view extends to the border with Sweden and Gaustatoppen mountain. The observation deck was closed in 2005 because of new fire safety regulations which would have required expensive modifications which coincided with rapidly declining visitor numbers. In the 1980s and 1990s annual visitor numbers averaged 100,000, but in the last year it was open to the public, only 25,000. There is a large underground shelter beneath Tryvannstårnet.

Øvresetertjern is a lake in Oslo, Norway. It is located 477 metres (1,565 ft) over sea level between the top of the hill Tryvannshøyden and Frognerseteren. From 1916 to 1938, the station Tryvandshøiden was located north of the lake, but it was never served by regular passenger trains.

Frognerseteren is a neighborhood of Oslo, Norway, located within Nordmarka. It is a popular starting point for recreational hiking and skiing in Oslo. Frognerseteren Station is the terminal station of the Holmenkollen Line of the Oslo Metro. Frognerseteren Restaurant (59°58′39″N 10°40′39″E) and conference facilities is one of the best examples of architectural style Dragestil in Oslo.Frognerseteren means the seter ("mountain dairy farm", roughly comparable to shieling) of Frogner (Manor). Frognerseteren with parts of the Nordmarka forest (Frognerseterskogen) was part of Frogner Manor until 1848, when the owner Jacob Benjamin Wegner sold the rest of the estate but kept Frognerseteren. Wegner's heirs sold Frognerseteren to Thomas Johannessen Heftye in 1864, and Heftye's heirs sold Frognerseteren to Christiania municipality in 1889. The restaurant menu is based on traditional Norwegian cuisine.

Tryvann stadion was a speed skating rink located at Tryvannshøyden in Oslo, Norway. Traditionally the main speed skating venues in Oslo was Frogner stadion and Bislett stadion. In 1933, the city council decided to build a skating rink at Tryvann to allow for a longer season. Unlike the city-center venues which were just above mean sea level, Tryvann stadion was located at 517 meters (1,696 ft) above mean sea level. This allowed the skating season to last from 1 November to 1 April. Transport was available via the Holmenkollen Line. During the 1952 Winter Olympics, the venue was designated as a reserve venue for Bislett, but never used. During the 1970s, the venue was demolished to make room for parking.