Mound and passage tomb
Cross section sketch of the passage
The Newgrange monument primarily consists of a large mound, built of alternating layers of earth and stones, with grass growing on top and a reconstructed facade of flattish white
quartz stones studded at intervals with large rounded
cobbles covering part of the circumference. The mound is 76 metres (249 ft) across and 12 metres (39 ft) high, and covers 4,500 square metres (1.1 acres) of ground. Within the mound is a chambered passage, which can be accessed by an entrance on the southeastern side of the monument. The passage stretches for 19 metres (60 ft),
 or about a third of the way into the centre of the structure. At the end of the passage are three small chambers off a larger central chamber, with a high
corbelled vault roof. Each of the smaller chambers has a large flat "basin stone", which was where the bones of the dead were possibly originally deposited, although whether it was actually a burial site remains unclear. The walls of this passage are made up of large stone slabs, twenty-two of which are on the west side and twenty-one on the east, which average out at 1½ metres in height;
 several are decorated with carvings (as well as graffiti from the period after the rediscovery). The ceiling shows no evidence of smoke.
The entrance passage to Newgrange, and the entrance stone
Situated around the perimeter of the mound is a circle of
standing stones. Twelve standing-stones survive out of a possible original thirty-five or thereabouts. Most archaeologists say they would have been added later, during the
Bronze Age, centuries after the original monument had been abandoned as a tomb.
Megalithic art on one of the kerbstones
The retaining wall and kerbstones
Newgrange contains various examples of
abstract Neolithic rock art carved onto it which provide decoration.
 These carvings fit into ten categories, five of which are curvilinear (circles, spirals, arcs, serpentiniforms and dot-in-circles) and the other five of which are rectilinear (chevrons, lozenges, radials, parallel lines and offsets). They are also marked by wide differences in style, the skill-level that would have been needed to produce them, and on how deeply carved they are.
 One of the most notable examples of art at Newgrange are the
triskele-like features found on the entrance stone. It is approximately three metres long and 1.2 metres high (10 ft long and 4 ft high), and about five tonnes in weight. It has been described as "one of the most famous stones in the entire repertory of
 Archaeologists believe that most of the carvings were produced prior to the stones being erected, although the entrance stone was instead carved in situ before the kerbstones were placed alongside it.
Various archaeologists have speculated as to the meaning of the decoration, with some, such as
George Coffey (in the 1890s), believing them to be purely decorative, whilst others, like
Michael J. O'Kelly (who led the 1962–1975 excavation at the site), believed them to have some sort of
symbolic purpose, because some of the carvings had been in places that would not have been visible, such as at the bottom of the orthostatic slabs below ground level.
 Extensive research on how the art relates to alignments and astronomy in the Boyne Valley complex was carried out by American-Irish researcher Martin Brennan.