The early medieval monasteries of the Columba family were decisively dependent on water as a natural boundary. In the Vita sancti Columbae Adomnán locates various monasteries with the help of lakes, while rivers elucidate bounds of rule and the sea forms the boundary of the world. As will be shown, in the Vita, water marks geographical areas, but it also defines social spheres like monastic areas of activity. As a compositorial element it serves to differentiate between geographical and social neighbourhood and, to distinguish here and there, us and the others.
During the Early and High Middle Ages the dār al-Islām had a suitable access to the Atlantic Ocean, stretching roughly from modern central Portugal to the far south of Morocco. In many medieval Arabic sources this ocean was seen as a boundary of Muslim expansion in the west as well as the end of the (known) world. But in contrast, some Arabic and even Latin documents allude to Atlantic activities of Muslim seamen, ranging from offshore fishing to maritime trade and naval warfare, which made this ocean to a zone of contact at least between northwest Africa and the Iberian Peninsula. Furthermore, a few Arabic sources dating from the 9th to the 14th century shed some light on the concepts, awareness and knowledge concerning the Atlantic Ocean and even indicate a growing interest in its exploration. So the aim of this paper is to reveal these Islamic roots of early Atlantic contacts and exploration.
In the 14th century Venice developed a political discourse aimed at justifying the Venetian thalassocracy, in particular within the 'gulf of Venice', delimited by the line Ancona - Zadar. This paper will thus study two tools developed by Venetians to claim dominion over such a vast area: the invention of a myth of the city origins, in which the Adriatic Sea played a crucial role, and which allowed them to claim it as a Venetian possession, and the real means deployed to substantiate such a claim, eg. the fleet. To conclude, both aspects will be crucial to understand how Venetians perceived the notion of borders and how it crafted the political decisions of the republic.