The archaeological sites Gradishte 2 and Gradishte 3 are located along the Haemus Motorway. The area was inhabited for a long period of time – from the late Neolithic–Chalcolithic period, Early Iron Age up to late antiquity. All excavated structures such as pits, dwellings, and EIA necropolis were situated in a similar type of sediments – clayey loess. Differences between the loess in these sites are the clay content, freshness, and roundness of quartz and feldspars. They are explained by different watershed areas, variations in the source area, and weathering intensity.