The fringe area of the Venice Lagoon has always been characterized by a significant diversity of environments, a changing landscape along a broad spectrum centred upon land and water as its main variables. From the high Middle Ages the Republic had been constantly trying to get control over these lands, mainly along internal waters and by using state-of-the-art scientific instruments and techniques. By the XV century a robust demand for a more precise knowledge of the territory had stimulated the search for accurate and reliable information to control and manage effectlively the Lagoon area. Even though currently the Republic is largely credited with such an effort, this paper aims to provide a different perspective by demonstrating that knowledge progressed more diffusely within the Venetian society, both at public and private levels. To get complete and reliable information on this area, also surveyors, landowners and religious communities realised that they had to get a view of it as if from above, using astrolabes, and map the land by making use of sophisticated tools and techniques to describe these territories. In fact, largely unexplored archive records show that monasteries acquired a fairly detailed knowledge of local geography, demonstrating that they were perfectly able to describe and have a hold over the environmental complexities of the Lagoon fringe area. By analysing a large number of records from the archives of several Lagoon monasteries, it is possible to assess how relatively advanced instruments and techniques for reliable landsurveying and topography were being tested, used and improved influencing the geographical and social space of Venice throughout the Middle Ages and contributing to boost agricultural productivity in the Terraferma.