Constructed during the Neolithic, cairns in the Severn-Cotswold tradition share several characteristics: an elongated trapezoidal (or wedge) shape up to 328 feet long; a cairn (a mound of deliberately placed stones or rocks erected as a memorial or marker); a revetment (retaining wall) of carefully constructed dry-stone walling that also defines a horned forecourt at the widest end; huge capstones supported by orthostats; and a chamber (or chambers) in which human remains were placed, accessible after the cairn was completed by way of a gallery (passageway).