Form of megalithic tomb in which a burial chamber set in the centre of a barrow is approached by means of a narrow passage. The barrow is usually round in plan, but other shapes are known. Most passage graves have a single chamber, but again variations are known, and some have up to ten chambers opening into a single barrow from different parts of the outer perimeter. There is also much variation in the shape and size of the chamber, round, square, rectangular, and polygonal forms being the most common. Some chambers have side cells opening off them. Passage graves are found in western France, Spain, the western parts of the British Isles, and Scandi‐navia. Various subtypes are known, including simple passage graves, developed passage graves, and multiple passage graves. The earliest passage graves date to about 4500 bc in Brittany; the tradition continues down to about 2000 bc in some areas.