Billown, near Castletown, is one of the most important Neolithic landscapes in the British Isles, brought to light after flint finds in 1995 led to long-running excavations by Bournemouth University. The site includes a stone circle, numerous standing stones, round barrows, a causewayed enclosure, a small ditch-and-bank 'mini-henge', cremation pits and a possible cursus monument, with finds including Ronaldsway-style pottery jars. Coordinates given are approximate (Billown estate area).