A hill fort is a type of earthworks used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are typically European and of the Bronze and Iron Ages. Some were used in the post-Roman period. The fortification usually follows the contours of a hill, consisting of one or more lines of earthworks, with stockades or defensive walls, and external ditches. Hill forts developed in the Late Bronze and Early Iron Age, roughly the start of the first millennium BC, and were in use in many Celtic areas of central and western Europe until the Roman conquest.