The Greek colonies were founded in areas of economic and geo-strategic interest. From this perspective, Histria benefited from the advantages offered by the sea, the delta (the Danube River) and the coastal zone. It also benefited from the continental resources within the hydrographic basin corresponding to the Razim-Sinoie lagoon complex. This study combines physical geography (especially geomorphology) and archaeological parameters to delimit, according to the deontological principles, the sphere of influence of the city of Histria and the manner of settlement of the Greek cities. The study delimits Histria's area of influence along the coastal fringe and hinterland. The principles behind the study (the delimiting of the hydrographic basins as areas of influence) represent a novel approach in Romanian archaeology. The closure of the Halmyris bay began around 3000 bp and the city of Histria ceased activity around 2000–1500 years bp. The coastal settlements were based on exploitation of marine resources as well as those provided by the land. When trying to delimit the area under the influence of the Greek city of Histria, one has to take into account the existence of geological and soil resources, but excluding local topography. Based on geomorphological and cartographic rules, as well as local considerations, the area served by the city was delimited. The limits follow the outline of the watershed closing the lagoon complex. From this perspective, three types of territory (horizons) were delimited. Each of the delimitations is based on geographic criteria: topography, resources and geo-strategy.