Barrows In Britain (4000 BCE and Later)

A well preserved barrow on Anglesey island, home of the last stand of Druids against the Romans in Britain.  
Stoney Littleton Long Barrow is located near the village of Wellow in the English county of Somerset. 
Chambered long barrows were constructed during the Neolithic between 4000 and 2500 BC. This one is thought to have been  constructed around 3500 BC.  The stone structure is about 30 metres (98 ft) in length and contains a 12.8 metres (42 ft) long gallery with three pairs of side chambers and an end chamber. 
The tomb was first opened around 1760 by a local farmer to obtain stone for road building. The site was excavated by John Skinner and Richard Hoare in 1816-17. The excavation revealed the bones (some burned) of several individuals. The mound was restored in 1858 by Thomas Joliffe. Some of the artefacts from the excavations are in the Bristol City Museum and Art Gallery.
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 Burial Mounds With Ritual Spaces

(February 14, 2024)  While burial mounds exist all around the world, those with temporarily accessible tombs inside mimicking caves and having ritual spaces outside are called barrows. They are most prominent in Druid culture. Barrows can be circular or be a long oval. All have some sort of central chamber and many have a ritual site outside their entrance where the powers of the ancestors can be called upon. 

Often these sorts of mounds would be surrounded by square stone slabs which in turn gave rise to stone henges which represented connections to ancestral powers often associated with death. Wood henges derive from observatories and had a different function of connecting to life powers and or astrological powers.