Both monuments are built at true scale in metres, with north up the screen in plan view. The sun is computed for the real latitude and longitude of each site, with atmospheric refraction, the sun's disc, and a modelled horizon. Shadows are cast by every stone, so the alignments emerge from the geometry rather than being painted on.
Sarsen circle: 30 uprights about 2.1 m wide, 1.1 m thick and 4.1 m tall, with an inner diameter of 29.6 m (97 ft), carrying a ring of 30 curved lintels whose tops sit about 4.9 m above the ground. Five trilithons rise towards the south-west, the Great Trilithon's upright standing 7.3 m. Inside sit a bluestone circle of about 60 stones (23 m across) and a horseshoe of 19 dressed bluestones, with the Altar Stone (4.9 m) before the Great Trilithon. The axis runs at 49.9°. Outside: the bank and ditch (about 110 m across, with entrances to the north-east and south), the 56 Aubrey holes, the four Station Stones on a rectangle of about 80 by 33 m, the Heel Stone 77 m out on the Avenue, the Slaughter Stone, the Avenue, and the Cursus to the north.
Stone numbering follows Flinders Petrie. Current-day state: 17 circle uprights and six circle lintels in place (101, 102, 105, 107, 122, 130), stones 13, 17, 18 and 20 missing, trilithons 51–52, 53–54 and 57–58 complete, 56 and 60 standing alone with 55, 59, 156 and 160 fallen. The leaning Heel Stone, the fallen Station Stone 91, the recumbent Slaughter Stone, Aubrey-hole markers, visitor path and A303 are shown.
Pristine shows the finished monument of about 2300 BC: a complete sarsen circle (supported by the 2013 parchmarks), freshly dressed pale sarsen, raw white chalk banks and ditches, the Heel Stone with its lost partner (stone 97), and the Slaughter Stone standing with a partner across the entrance.
Mound about 85 m across and 13.5 m high, ringed by 97 kerbstones; K1, the entrance stone, carries the triple spiral. The 19 m passage rises about 1.6 m towards a cruciform chamber with a corbelled roof about 6 m high. The roof-box above the doorway admits the midwinter sunrise along the passage to the chamber floor; in Pristine the doorway is sealed by its closing stone, so only the roof-box beam gets in. Current day shows the 1970s quartz-and-granite facade; Pristine shows a cairn front with quartz spread on the forecourt, one of the alternative readings of the excavated evidence.
Ancient epochs use the obliquity of the ecliptic for that date (Laskar's series: about 23.97° in 2500 BC and 24.04° in 3200 BC, against 23.44° today), so solstice sunrises sit measurably further round than now. Clock times are local solar time for ancient epochs and GMT, BST or IST for the present day. Lunar lines show the major standstill extremes, with lunar parallax.
The resting places of fallen stones, which bluestone remnants survive, the Great Circle's centre, the barrow groups, King Barrow Ridge trees, the A303 route, the Boyne's course, the far horizon profiles and the chamber's detailed plan are representative rather than surveyed. Ancient-epoch seasons use the modern calendar mapping, so dates are good to about a day.