Greencastle Hill is the remnant of an isolated volcano which was exposed to wave action at the beginning of the Oligocene period due to the subsidence of the island of Antigua.  An array of close-fitting rhomboidal and polygonal columns was formed during the contraction of slowly cooling lava flows and subsequent erosion produced a plateau strewn with rocks and boulders.

These stone features include the “megaliths” and “sacrificial slabs” which are considered by some authorities to be the remains of a prehistoric astronomical observatory and temple. The possibility was explored in the New York Times March 14, 1971, in an article entitled: “Antigua’s Tropical Stonehenge”. Other authorities, including geologists, consider the “megaliths” to be purely natural formations, although there is some agreement that the naturally occurring features could have been positioned and worked by human-kind.

A survey of the site was done in March 2001 in order to determine if this area could possibly have been of significance as a religious or celestial observatory. Results of the survey indicated correlations between the azimuths of the investigated stones and those of celestial bodies. Also of interest was of correlations found with the bearings of the “female stones”; two stones in a “V” shape suggesting female imagery. Further research needs to be done, but at this time the possibility of a “Tropical Stonehenge” is well within the bounds of possibility!

Situated on a low round hill on the south west entrance to St. John's Harbour, Goat Hill was a strategic point on the west coast of Antigua.  Construction of the initial defense works began about the same time as Fort James on the northern side of the harbour.  It is a unique fort in its design and also has the distinction as the only fort on Antigua to have seen enemy action and to have fallen to invading forces, twice.

In 1652, Goat Hill was the dramatic site of the exploits of the debonair Prince Rupert, grandson of James I and the first member of the royal family to visit the West Indies.  Hoping to capture Antigua for the Royalist cause, the Prince and Sir Robert Holmes captured the fort at Goat Hill and raided two of the Parliament's vessels anchored in Deep Bay below.  The early fort with its a single gun was taken during the night by Sir Robert and the Prince attacked from the sea by daylight.  One Commonwealth ship was sunk in the bay and the other was captured and taken to Montserrat.

In 1666, a French military force landed in Deep Ray and took Goat Hill.  At that time, there were eight guns at the site.  They also captured the crude defense platform at Galley Bay, which had six guns mounted on earth- mounds. The English left Goat Hill so quickly that they left the Royal flag still flying.  Antigua was returned to the British the next year with the Treaty of Breda.

During its time as a military platform, it acquired several names.  The 1704 return of forts shows that "Cripplegate" (Goat Hill Fort) was still only a platform and that Major Thornton, Captain Martin and John Hadden were it's officers.  In 1716 Oliver's

History states that it was to be improved and a battery was to be constructed and by 1734 Governor Mathews reports that there were seven guns mounted at the fort.

In 1779, Goat Hill was strongly fortified by the Admiral Barrington whose name the fort bears today.  Admiral Barrington had defeated the French off St. Lucia in 1778.  This was an anxious time for the British, having just lost several islands to the French, and, like Shirley Heights fortifications at English Harbour, Fort Barrington was strengthened to forestall attack by the French Forces.

An anonymous writer in 1781 describes Goat Hill as "a round eminence containing a stone fort".  At the entrance to the fort there are two stone tablets dedicated to William

Burt and his daughter.  Burt was governor from 1776-81.  The Captain of the Fort in 1823 was Charles Matthews and twenty years later was William Thibou and the Sub-gunner, Robert Jaggard.  At this time the fort was known as the Queen's Battery at Goat Hill.

Although Fort Barrington was built as a fort, it's was also an important Signal Station, reporting on ship's movements.  The signals were repeated by other forts on the island; a early and effective communication system.  The Antigua Almanac for 1843 gives the complete list of signals, examples being, no 534 Suspicious Sail to the South: no 456 Boat Upset on Sandy Island.  Goat Hill has continued to be a signal station for the Harbour Department up to about 1960, though then an earth return telephone was used instead of the signal flags.  Today a circular stone gun platform survives, beneath which is an elegant staircase that leads to the interior powder magazines.  Fort Barrington is now a National Park.