We are going to be spending a week or so in Salamanca and I would like to try to make a side trip to Portugal for maybe a long weekend. It doesn't seem like train or bus will fit into our schedule, from what I've seen there are only a few routes from Salamanca and they take a very long time. We were thinking of renting a car in Salamanca (also returning there to drop the car off). Can anyone tell me how long of a drive it is to either Coimbra or Porto? Or is there another city closer to Salamanca that would be worth the trip?