A small country situated in the heart of Pyrenees, completely overwhelmed with its neighbors: France and Spain, is a difficult one to visit. There are always airplanes, buses and trains heading towards Andorra, but not many actually end up there. Because of its size (or the lack of it), it doesn’t have an airport so if you decide to take a trip to these mountains, your best choice would be starting from either Barcelona or Toulouse. Both of them less than 200km away. On the other hand, if you decide to take the train, you will end up quite close to the country itself: from the Spanish side, the closest train station is the one in Puigcerda (around 80km from Andorra), while on the French side you will be luckier with L'Hospitalet (only 3km from the border), from where you have buses heading to Andorra every 30minutes. If you're not willing to spend much money but still want to maintain comfort – both countries have a well-developed system of car-sharing, called Blabla car with many people heading in and out of Andorra. If that is too expensive – hitchhiking is your best bet. If you're lucky enough to get a ride, that is. If you decide for the latter – definitely aim at petrol stations rather than signs-by-the-road approach, since establishing contact will get you a ride easier.
Small? Who cares.. it is worth to see Andorra!