Why are the artefacts at Vindolanda found in such good condition? A combination of factors aid the preservation and superb condition of the finds. The main aid is that the ground has anaerobic conditions, which means that there is no oxygen in the pre-Hadrianic excavation layers. Roman builders spread clay and turf over demolished buildings before starting new building programmes on a previously used site. This effectively ‘capped’ the underlying layer preserving everything left beneath it. Artefacts like leather, wood, textiles and writing tablets and metal objects survive in near perfect condition. After conservation they are stabilized and ready for research and display. At the higher Vindolanda levels the conditions are not anaerobic. The organic finds do not survive at this level and metals are highly corroded due to the presence of oxygen and bacteria.