Looking at the terrain of Iberia, there are many rough geographical features. However, many polities which existed in the peninsula made great use of horses for war, ex: Umayyad, Almoravid, Castille. Why is it that such a hilly area became dominated by states with an emphasis on horseback riding?
This is not a history-related answer, but while Iberia does have many mountain ranges, a large part of its surface is flat highlands. Castille in Particular is a large plain divided in two parts by the Sistema Central range and bordered by several others. Outside of this large central area, the Ebro and Guadiana rivers also form large, mostly flat valleys.
