The archaeological site in England formed by a circle of standing stones that is a World Heritage Site is Stonehenge.
Stonehenge stands on Salisbury Plain in Wiltshire, about 13 kilometres west of Salisbury. Its construction unfolded over many centuries: the earliest ditch and bank date to around 3100 BC, while the famous arrangement of large sarsen stones was erected roughly between 2600 and 2400 BC. The monument was used and modified into the Bronze Age.
The outer stones were shaped with sophisticated mortise-and-tenon and tongue-and-groove joints. Smaller bluestones were brought from the Preseli Hills in Wales, around 240 kilometres away, showing that prehistoric communities moved massive stones over remarkable distances. The monument’s layout is aligned with the solstices, though its exact purposes remain debated.
Stonehenge was inscribed in 1986 as part of the Stonehenge, Avebury and Associated Sites World Heritage Site. Avebury is therefore a related World Heritage monument, not the single best answer to this question. The Carnac Stones and Malta’s megalithic temples are separate prehistoric sites.