A former kingdom, Castile ( IPA: or ), gradually merged with its neighbors to become the Kingdom of Spain. In modern-day Spain, it is usually considered to comprise the regions of Castilla y León in the north-west, and Castilla-La Mancha and Madrid in the center and south of the country. However, there are different versions about the exact boundaries of Castile. Modern Spanish monarchs are numbered according to the system of Castile.
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