 Large cities, especially Seville, Valladolid and Barcelona, had significant Jewish populations centered on Juderia, but in the coming years the Muslims became increasingly alienated and relegated from power centers.Post-reconquest medieval Spain has been characterized by Americo Castro as a society of relatively peaceful co-existence ("convivencia") punctuated by occasional conflict among the ruling Catholics and the Jews and Muslims.However, as historian Henry Kamen notes, the "so-called convivencia was always a relationship between unequals."