Grimsbury Castle is an Iron Age

Iron Age

The Iron Age is the archaeological period generally occurring after the Bronze Age, marked by the prevalent use of iron. The early period of the age is characterized by the widespread use of iron or steel. The adoption of such material coincided with other changes in society, including differing...

 "multiple enclosure" Hill Fort

Hill fort

A hill fort is a type of earthworks used as a fortified refuge or defended settlement, located to exploit a rise in elevation for defensive advantage. They are typically European and of the Bronze and Iron Ages. Some were used in the post-Roman period...

 comprising a large circular encampment situated on a high hill. It is situated within Grimsbury Wood to the between Cold Ash and Hermitage

Hermitage, Berkshire

Hermitage is a village and civil parish, near to Newbury, in the English county of Berkshire.-Location and communications:The civil parish is made up of a number of settlements: Hermitage village, Little Hungerford and Wellhouse, in 2003 these consisted of some 1,154 people in 444 houses, although...

, in the county of Berkshire

Berkshire

Berkshire is a historic county in the South of England. It is also often referred to as the Royal County of Berkshire because of the presence of the royal residence of Windsor Castle in the county; this usage, which dates to the 19th century at least, was recognised by the Queen in 1957, and...

History

The site benefits from a natural spring which reportedly has never been known to run dry. The entrenchment

Entrenchment

Entrenchment or Entrenched may refer to:* Military trenches with relation to Trench warfare, especially that of World War I *Entrenchment as a feature of a Constitution, making it more difficult to amend* Entrenched clause within a constitution...

 would appear to have been extended on the South side of the hill for the purpose of enclosing this spring. This rampart

Defensive wall

A defensive wall is a fortification used to protect a city or settlement from potential aggressors. In ancient to modern times, they were used to enclose settlements...

 appears to have had only two entrances, one on the North and the other on the South side; just within the entrenchment, at the entrance on the North, is a small tumulus

Tumulus

A tumulus is a mound of earth and stones raised over a grave or graves. Tumuli are also known as barrows, burial mounds, Hügelgrab or kurgans, and can be found throughout much of the world. A tumulus composed largely or entirely of stones is usually referred to as a cairn...

, which may have been constructed as a mount for observation or defense, or for the purpose of interment.

The name shows that the later Saxon settlers in the region found the earthworks

Earthworks (archaeology)

In archaeology, earthwork is a general term to describe artificial changes in land level. Earthworks are often known colloquially as 'lumps and bumps'. Earthworks can themselves be archaeological features or they can show features beneath the surface...

 so impressive that they thought they must have been built by the chief of their gods, Woden alias Grim.

The site lies at an elevation of 155m AOD. There is an 18th Century Folly

Folly

In architecture, a folly is a building constructed primarily for decoration, but either suggesting by its appearance some other purpose, or merely so extravagant that it transcends the normal range of garden ornaments or other class of building to which it belongs...

on the site, also known as Grimsbury Castle.

Today the site is crossed by a small single track roadway.