Castilla y León is the largest autonomous community in Spain — in fact, it is the largest subnational political division in the European Union. It is formed by the union of two ancient kingdoms: Old Castile (Ávila, Burgos, Segovia and Soria) and the Kingdom of León (León, Zamora, Salamanca, Palencia and Valladolid), which were separated and reunited several times in the Middle Ages. If you want to learn "true" Castillan Spanish (lisp and all), check out the Universidad de Salamanca, founded in 1218 by Alfonso X of León (making it one of the first in the world!). And while you're there, be sure to find "la rana" in the entrance to the University. It might take you a while!