Lake Saimaa is the largest lake in Finland and the fourth largest in Europe. The complete waterway system, of which Lake Saimaa forms a part, consists of a vast group of lakes that can be sailed all the way up to several towns in the north. The Saimaa Canal, on the other hand provides an important waterway from Lake Saimaa, down to the Baltic Sea in the south. Lake Saimaa empties its waters, via River Vuoksi, into Lake Ladoga in Russian Karelia and from there into the Gulf of Finland, via the River Neva. The water of Lake Saimaa – characterised by its brownish colour – is naturally poor in nutrients, but rich in humus. The quality of the water is, for the main part, good: it is suitable for swimming and, in many areas, also for domestic use.