A type of later Neolithic burial monument found in clusters along the Atlantic coastlands of northwest Europe, notably in central Ireland, North Wales, and Orkney. Dating mainly to the 3rd millennium bc, these structures represent enlarged or developed versions of the earlier simple passage graves. They typically comprise a large round mound of earth and stone more than 35 m in diameter, within which there is one or more stone‐built chambers accessible from the outside of the mound via a long narrow passage. The chambers are usually square, rectangular, or polygonal in plan and often show structural compartmentalization with side cells opening from the main chamber. Burials either by inhumation or cremation were made in the side cells. The walls of the passage and chamber often carry passage grave art, as do the stones forming the kerb around the outside of the mound in some examples. Decorated stones brought from elsewhere are sometimes broken up and used in the construction of developed passage graves. In a number of examples the passages are aligned such that the rising or setting mid‐winter sun shines into the central chamber for a few days each year. The largest and best‐known examples are those in central Ireland, such as Newgrange and Knowth. See also multiple passage grave; passage grave.