A kistvaen or cistvaen is a tomb or burial chamber formed from flat stone slabs in a box-like shape. If set completely underground, it may be covered by a tumulus. The word is derived from the Welsh cist (chest) and maen (stone). The term originated in relation to Celtic structures, typically pre-Christian, but in antiquarian scholarship of the 19th and early 20th centuries it was sometimes applied to similar structures outside the Celtic world.