Clay-illuvial soils with argic horizon and developed from loess or other silty deposits constitute high-quality arable land owing to favourable physical and chemical properties,. There are thus numerous reports on such soils, considering their structure, compaction, erosion, water and air properties. However, there is still a lack of quantitative studies on structure and physical properties on analogous soils under forests. The aim of this research was therefore a comprehensive description of the physical state, including structure, water and air properties, of a forest Retisol developed from loess. Morphographic, morphological and morphometric parameters of structure, selected physicochemical and water and air properties and also relationships among the obtained parameters were analysed for genetic horizons O, Ah, AE, E, Bt/E, Bt, BtC and C. The field survey and soil structure images indicated that the studied forest soil had an undisturbed sequence of genetic horizons. The soil structure was shaped by soil flora and fauna causing bioturbation. Qualitative and quantitative structure analysis revealed that the O horizon had a loose arrangement, the Ah horizon had an aggregate crumb structure, the AE horizon had zones of an aggregate crumb structure and non-aggregate structure (fissured or with channels), while the remaining mineral horizons showed essentially a non-aggregate structure with varying proportions and sizes of planes and biogenic pores (i.e. cracked or fissured structure and structure with channels, respectively). The morphometric and physicochemical parameters facilitated a detailed analysis of the Retisol’s physical state. The Retisol’s structure type and degree of aggregate development directly influenced its hydraulic conductivity and water retention capacity. Therefore, under simulated precipitation, the soil water content and effective saturation varied mainly in the topsoil (O–E horizons) and virtually no changes were observed in the subsoil (Bt–C horizons). The research resulted in a comprehensive analysis of the physicochemical and morphometric parameters, their relationships, and structure images that were previously unavailable in other studies, covering the physical state of the entire pedon of a forest Retisol. The results obtained may serve, for example, as a reference (control) for analogous soils located in non-forest ecosystems and become an element in space-for-time substitution scenarios aimed at assessing the intensity of anthropogenic transformation.