At the dawn of the Early Modern Period, the marriage and joint rule of Isabella I of Castile and Ferdinand II of Aragon in 1469 marked the "de facto" unification of Spain, joining what contemporaries referred to as "the Spains". After the conquest and fall of the Kingdom of Granada, the last Muslim-ruled polity in the Iberian Peninsula (see Reconquista) in January 1492, the Hispanic Monarchs, Isabel and Fernando, soon after getting the title of « Catholic King and Queen » from Pope Alexander VI, agreed to undertake the charting of a new commercial maritim route to Asia sailing westwards through the Mare Tenebrosum (medieval name for Atlantic Ocean), a project proposed to them by Christopher Columbus, a Genovese navigator and cartographer. This move was provoked by the control of the historical land and maritime spice trade routes by the Ottoman Empire pursuant to the conquest of Constantinople (today's Istanbul) and the end of the Eastern Roman Empire.