This study examines the arachnoid fossae (AF) in crania from early modern Wrocław, Poland, and their connection to endocranial lesions, specifically abnormal blood vessel impressions (ABVI) and periosteal appositions of the dura mater (PADM). AF are fovea on the inner surface of the cranial bone, which arise as the result of arachnoid granulations' (AG) protruding and causing the resorption of the bone. ABVI and PADM are non-specific pathological lesions caused by inflammation and hemorrhages in the meninges. The goal of the study is to determine if the size of AF is associated with the occurrence of endocranial lesions (ABVI and PADM), whether they can aid in diagnosing pathological conditions in historical populations, and to propose a measurement methodology. Using an endoscopic device, the study analyzed 80 adult crania from a collection in Wrocław, Poland. The size of AF was measured using scaled photographs, and the occurrence and severity of ABVI and PADM were also documented. The study then investigated the relationship between the size of AF and the presence of ABVI and PADM. It was determined that the individuals with ABVI had greater AF than those without the lesions. The results indicate that while the presence of AF can be considered a normal cranial variation, their size may be useful in diagnosing pathological conditions in the meninges, such as trauma, tumors, or infectious diseases.