At Hayl Ajah, a sediment-filled karst depression at 1000 m a.s.l. in the middle part of the Al-Hajar Mts (Oman), stone artefacts were found both in situ and scattered on the surface by the Masaryk University Project SIPO. Some of these artefacts belong techno-typologically to the Late Neolithic - a period of drier climatic conditions. Other artefacts, found in situ, have no clear analogies on the Arabian Peninsula yet. This raises the question, whether the mountain range may have served as an area of retreat for prehistoric humans during periods of climate deterioration (Al-Hajar Refugium Hypothesis). Using geological, palaeoenvironmental and archaeological proxy data, the multidisciplinary project will check whether certain karst rocks (e.g. limestones) in interplay with accumulations of windblown sediments could have provided prehistoric humans with a threshold level of humidity also during phases of extreme dryness. This hypothesis can be tested at the open-air archaeological site Hayl Ajah that owns a sediment geoarchive reaching back at least 30 ka.