There isn't one.
Your best bet is, take a mainline train to Toulouse. (fairly flat country, lots of vineyards). Then a branch-line to "l'Hospitalet-pres-de-l'Andorre". Keep your eyes open for...
Spain and France have a common border. Along PART of that border is the tiny country of Andorra. On the north side of Andorra is France and on the south side is Spain. A border is a line between one...