In brief
Megalithic structures are considered together with the surrounding prehistoric sites.
Useful to know
Stonehenge and Avebury in Wiltshire are two different megalithic complexes. UNESCO connects them to nearby Neolithic sites and notes that the astronomical significance of the arrangement continues to be explored. [1]
In a plan, compare the distances and organization of the stones, instead of perceiving each structure as a uniform stone circle. The territory between the individual places is also important. Do not attribute a certain function to each opening only by its orientation: observed geometry and proven historical purpose are different things.
Sources
For further detail and to check the information: