what sites are close to the train station?
A great part of the green line is near the train station, just follow the signs
Coming out of the station take the "Sortie Nord" and right opposite is the "Jardin des Plantes". If that doesn't interest you turn left upon coming out of the station and a couple of hundred metre along is the "Chateau des Ducs de Bretagne". If you carry on in the same direction you will come to the old town.