The Stonehenge (World Heritage site) that visitors see today is considerably ruined, many of its stones having been pilfered by medieval and early modern builders (there is no natural building stone within 13 miles 【21 km】 of Stonehenge); its general architecture has also been subjected to centuries of weathering. The monument consists of a number of structural elements, mostly circular in plan. On the outside is a circular ditch, with a bank immediately within it, all interrupted by an entrance gap on the northeast, leading to a straight path called the Avenue. At the centre of the circle is a stone setting consisting of a horseshoe of tall uprights of sarsen (Tertiary sandstone) encircled by a ring of tall sarsen uprights, all originally capped by horizontal sarsen stones in a post-and-lintel (post-and-lintel system) arrangement. Within the sarsen stone circle were also configurations of smaller and lighter bluestones (igneous rock of diabase, rhyolite, and volcanic ash), but most of these bluestones have disappeared. Additional stones include the so-called Altar Stone, the Slaughter Stone, two Station stones, and the Heel Stone, the last standing on the Avenue outside the entrance. Small circular ditches enclose two flat areas on the inner edge of the bank, known as the North and South barrows, with empty stone holes at their centres.

The modern interpretation of the monument is based chiefly on excavations carried out since 1919 and especially since 1950. Archaeological excavations in the latter part of the 20th century suggest three main periods of building—Stonehenge I, II, and III, the last divided into phases.

Stonehenge I was used for about 500 years and then reverted to scrubland.

During Stonehenge II, about 2300 BC, the complex was radically remodeled. About 80 bluestone pillars, weighing up to 4 tons each, were erected in the centre of the site to form what was to be two concentric circles, though the circles were never completed. (The bluestones came from the Preseli Mountains in southwestern Wales and were either transported directly by sea, river, and overland—a distance of some 240 miles 【385 km】—or were brought in two stages widely separated in time.) The entranceway of this setting of bluestones was aligned approximately upon the sunrise at the summer solstice, the alignment being continued by a newly built and widened approach (the Avenue), together with a pair of Heel stones. The double circle of bluestones was dismantled in the following period.

In the second phase of Stonehenge III, which probably followed within a century, about 20 bluestones from Stonehenge II were dressed and erected in an approximate oval setting within the sarsen horseshoe. Sometime later, about 1550 BC, two concentric rings of holes (the Y and Z Holes, today not visible) were dug outside the sarsen circle; the apparent intention was to plant upright in these holes the 60 other leftover bluestones from Stonehenge II, but the plan was never carried out. The holes in both circles were left open to silt up over the succeeding centuries. The oval setting in the centre was also removed.

The final phase of building in Stonehenge III probably followed almost immediately. Within the sarsen horseshoe the builders erected a horseshoe of dressed bluestones set close together, alternately a pillar followed by an obelisk followed by a pillar and so on. The remaining unshaped 60-odd bluestones were set as a circle of pillars within the sarsen circle (but outside the sarsen horseshoe). The largest bluestone of all, traditionally misnamed the Altar Stone, probably stood as a tall pillar on the axial line.

About 1100 BC the Avenue was extended from Stonehenge eastward and then southeastward to the River Avon (Avon, River), a distance of about 9,120 feet (2,780 metres). This suggests that Stonehenge was still in use at the time.

Stonehenge and the nearby circular monument of Avebury were collectively added to UNESCO's World Heritage List (World Heritage site) in 1986.