Caption: A little on the geology and structure of Stonehenge: "Map of the central stone structure at Stonehenge as it survives today. Stone numbers are those conventionally used in the recent literature and following Flinders Petrie (1853--1942) in 1880.

Note that the term "Sarsen" used on the key refers to the hard silicified tertiary rock local to the chalkland of the Stonehenge region (i.e., Salisbury Plain). Sarsen is an exceptionally obdurate form of sandstone. The reference to sandstone on the key is to other non-sarsen material. The term bluestone conveniently, though somewhat controversially, describes a generic group of igneous rock exotic to Salisbury Plain. The major group of bluestones visible today are dolerite whose provenance is thought to be southwest Wales. A number of other igneous rocks are represented within the arrays." (Slightly edited.)

A little on the history of Stonehenge:

1. The complete Stonehenge was built and used over a period from about 3100 BCE to about 1600 BCE (see Wikipedia: Stonehenge: Early history) with the main construction of the big features (i.e., inner ring and the trilithons) sometime in the period 2600 BCE to 2400 BCE (see Wikipedia: Stonehenge: Stonehenge 3 II (2600--2400 BC)).

2. The constructors were Neolithic Britons and Bronze Age Britons, NEITHER of whom were Celts.

   It is NOT clear when and how rapidly the Insular Celts arrived or arose from cultural transmission from mainland Europe in the Hiberno-British Isles. Probably after 1000 BCE. See Wikipedia: Insular Celts: Celtic settlement of Britain and Ireland for an inconclusive discussion.

   It is the Insular Celts and at least some of rest of the Celts who had Druids---who did NOT build Stonehenge---and did NOT insofar has we know carry demonic rites there---despite what is suggested in Night of the Demon (1957 film).

3. In many ways, we know little about the Neolithic Britons and Bronze Age Britons. We do NOT know their language and there is NO textual history. All we have is the archaeological record.

4. Stonehenge acquired its modern name in Anglo-Saxon England and probably means stones hanging in air, but the possibility exists that it means stones for hanging: i.e., gallows (see Wikipedia: Stonehenge: Etymology).

5. Since circa 2000, we know a lot more from archaeology about Stonehenge than we ever imaged we could before. All the tools of modern archaeology have been thrown at it principally by the Stonehenge Riverside Project (fieldwork 2003--2009). One of the directors of the project is Mike Parker Pearson (1957--).
   If you arn't mad when you start working on Stonehenge, you soon will be.
   ---an approximate quotation from Mike Parker Pearson (1957--), approximately quoting someone else, 2016 May01 less a few days, public talk at UNLV.

6. In 2020, the origin was identified for most of the largest megaliths of Stonehenge, the Sarsen stones, which form the inner ring of standing stones with lintels and the horseshoe pattern of 5 huge trilithons within that ring (see Wikipedia: Stonehenge: Stonehenge 3 II (2600--2400 BCE)). They came from West Woods, now a small forest near Marlborough, Wiltshire, 25 km north of Stonehenge (see Wikipedia: Stonehenge: Origin of sarsens identified).

   You may well wonder how the Stonehengers transported the Sarsen stones. Modern experiments suggest that they slid the Sarsen stones on logs parallel to the direction of motion perhaps using animal fats (Wikipedia: Lubricant: History) as a lubricant. The Sarsen stones CANNOT have been rolled on logs: the logs just lock on each other. It probably took the Stonehengers a long time to move the Sarsen stones. They probably spent decades building the inner ring and the trilithons.

Credit/Permission: © Anthony Johnson, 2008 (uploaded to Wikimedia Commons by User:Sitehut, 2008) / CC BY-SA 3.0.
Image link: Wikimedia Commons: File:Stone Plan.jpg.
Local file: local link: stonehenge_map_modern.html.
File: Stonehenge file: stonehenge_map_modern.html.