The department is named after its two main rivers, the Ille and the Vilaine, whose confluent is in Rennes, the capital of the department and of the region; other important rivers include :
The department is moderately elevated above the level of the sea, with many hills; however the central part has a dense network of many small rivers connecting to the Ille or the Vilaine from all around the large bassin of Rennes. The elevated hills bordering this bassin are covered by several old forests now exploited by men for the production of wood. The bassin itself is a rich agriculture area, as well as the north-west of the department near the Rance.
In the extreme south of the department the flows of the Vilaine are going through slow decrease of elevation in a small corridor in the area of the city of Redon; in this area, the Vilaine is known for its frequent floodings during its recent history, often because of too intensive draining of agricultural areas around Rennes (some floodings have also affected some quarters of Rennes up to the 1980's due to incorrect management of old equipments of the artificial channel of Ille-et-Rance). To avoid these hazards within inhabited cities, some natural fields bordering the Vilaine in the south of the department are now left floodable, and works for regulating the level have been done including, small articicial lakes with derivation channels, replanting trees in the bassin, better management of forests, and regulating the articifial drains made for agriculture.
Today, Breton is again spoken due to schools teaching Breton, and due to a small immigration from Western Brittany to Eastern Brittany, where there are more cities, so where there's more work. A recent study shows that the Breton speakers in this region represent 3,3% of the total number of Breton speakers. Interestingly, the Breton speakers aged 18-30 in this region represent 12,7% of the total number of Breton speakers of that age group. This is because there are relatively little elder speakers, but many people are learning the language. The study says that about 1.800 people are learning it (this includes one Diwan school in Rennes, some bilingual public and catholic schools, and evening courses).