Lohjanjärvi is a lake in Uusimaa

Uusimaa

Uusimaa, or Nyland in Swedish, is a region in Finland. It borders the regions Finland Proper, Tavastia Proper, Päijänne Tavastia and Kymenlaakso...

 region in southern Finland

Finland

Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

. The biggest part of the lake is located in the town of Lohja

Lohja

Lohja , is a town and municipality of Finland.It is located in the province of Southern Finland and is part of the Uusimaa region. The town has a population of and covers an area of ofwhich is water...

 and smaller parts in the municipality of Karjalohja

Karjalohja

Karjalohja , or Karislojo in Swedish is a municipality of Finland.It is located in the province of Southern Finland and is part of the Uusimaa region. The municipality has a population of and covers an area of of which is water...

 and in the town of Raasepori . The lake drains into the Gulf of Finland

Gulf of Finland

The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn...

 trough the Mustionjoki River (aka Karjaanjoki). Together with Hiidenvesi

Hiidenvesi

Hiidenvesi is the second largest lake in the Uusimaa region in Finland. The biggest part of the lake is located in the municipality of Vihti and smaller parts in the municipality of Nummi-Pusula and in the town of Lohja...

that drains into it from north it is part of Karjaanjoki basin.