Endoscopic anatomy differs from microsurgical anatomy. Topographical orientation as well as the proportion of objects, is different as they depend on the lens/object distance. Orientation under endoscopic conditions requires structures with defined positions or recognisable structures previously identified radiolologically. Structures are anatomical landmarks if the topographical relation to their surroundings is constant and they are easy and reliable to recognise. The contents of the dural sack are nerve roots with their supplying vessels, arachnoid trabeculars, filum terminale, and CSF. Safe navigation of a thecaloscope in relation to the bony structures is only possible with the simultaneous use of intraoperative fluoroscopy. To facilitate the navigation of scopes and instruments in the subarachnoid space we attempted to identify and describe reliable, and therefore constant recognisable anatomical landmarks.