transport line started construction in 2010 and its first stage was taken into use on 18 November 2017. Geography General Espoo has an area of — (59%) of land and (41%) of water. Sea water makes up 37% of the total area of Espoo and inland water makes up a bit over 3%. To the north of the lush river areas and the fields in central Espoo, the archipelagal and coastal zone in southern Espoo changes into lake-filled and rocky terrain. At some places the lake areas in northern Espoo resemble the Finnish Lakeland. The largest part of the lake ridge in Nuuksio is located in Espoo, but a part of it is located in neighbouring Vihti. The largest lakes in Uusimaa, Lohjanjärvi and Hiidenvesi, are located west of the ridge. The highest point in Espoo is Velskola at 114.2 m above sea level, and the lowest point is at sea level. Espoo is a part of the Greater Helsinki metropolitan region and is contiguously bordered by the cities, towns and municipalities of Kirkkonummi, Vihti, Nurmijärvi, Vantaa, Kauniainen and Helsinki. For a city of its size, Espoo is home to exceptionally large natural areas. The southern part of the city is characterized by maritime environment, including a varied coastline and an archipelago consisting of 165 islands. Bedrock The minerals and structures of the rocky and hilly topography of Espoo were formed about 1880 to 1650 million years ago. Particularly the Weichselian glaciation has had an effect on the current environment - the continental ice sheet withdrew from what is now Espoo about 13 thousand years ago. The first areas to surface from underneath the sea were the high hills in northern Espoo, such as Mustankorvenkallio. The numerous smooth cliffs on the seashore and in the archipelago were caused by wear by the continental ice sheet; there are grooves on their surfaces, indicating the direction of the flow of the ice sheet. Icebergs split off from the ice sheet have transported glacial erratics, including those in Kunnarla, Soukka and Suomenoja. Main minerals in the Espoo bedrock include gneiss, migmatite, granite, gabbro, amphibolite and mica schist. Rare orbicular granite can be found in Nuuksio, the deposit is internationally valuable. At many places there are thick layers of clay on top of the bedrock, and fields were plowed onto clay-covered valleys. The thickness of the clay layers was mainly formed in the Baltic