Wadi Hariq is a complex valley system in the Northwest Sudan about 400 km west of the Nile. Stratigraphic investigations provide new data on the environmental and climatic history of the present-day hyperarid centre of the southeastern Sahara. Archaeological work there only started at the end of the 1990s, with a survey and excavations carried out as part of the multidisciplinary research project ACACIA of the University of Cologne. To date, 104 sites are known in the Wadi Hariq. Based on the pottery found at these sites, most can be attributed to the Handessi Horizon, the former Geometric Pottery Horizon, of the eastern Sahara. Geometric patterns, and also mat impressions, are characteristic of the Handessi Horizon (ca 2200 . 1100 BC). The subsistence of these prehistoric inhabitants was based on the herding of cattle and small livestock. Transhumance cycles included areas further north (Laqiya region) and south (Wadi Howar), and perhaps even the Nile Valley has to be considered. Similar decorative patterns have been found in all these areas. Evidence of an even earlier human presence in the Wadi Hariq during the Holocene is provided by several sherds decorated with Dotted Wavy Line and Laqiya-type patterns as well as some fragments of rippled-ware pottery.