Since a peninsula is just an extension of a larger landmass, isn't the exact line dividing the "peninsula" from the rest of the land mass somewhat arbitrary? It seems like it's arguable whether Andorra is on the peninsula or not. Looking at a map, it seems to me like you could draw the line between Bayonne, France, to Tarragona, Spain, leaving Andorra out. Conversely, you could draw the line between Bayonne and La Palma (just south of Narbonne), which would include a decent chunk of France. Disclaimer: I am not a geographer.