Archaeologists have differentiated these Early Neolithic tombs into a variety of different architectural styles, each typically associated with a different region within the British Isles. Passage graves, characterised by their narrow passage made of large stones and one or multiple burial chambers covered in earth or stone, were predominantly located in northern Britain and southern and central Ireland. Alternately, across northern Ireland and central Britain long chambered mounds predominated, while in the east and south-east of Britain, earthen long barrows represented the dominant architectural trend. These earthen long barrows were typically constructed of timber because building stone was scarce in southern Britain; archaeologist Aubrey Burl argued that these timber tombs might have been "even more eye-catching" than their stone counterparts, perhaps consisting of "towering carved poles, flamboyantly painted", but that evidence of such sculptures has not survived.