To the north, just outside the bounds of the Ráith na Rig, is a ringfort with three banks known as Ráith na Seanadh (the Rath of the Synods). Excavations of this monument have produced Roman artifacts dating from the 1st-3rd centuries.
Further north is a long, narrow rectangular feature known as the Banqueting Hall, although it is more likely to have been a ceremonial avenue or cursus monument approaching the site, and three circular earthworks known as the Sloping Trenches and Gráinne's Fort. All three are large ring barrows which may have been built too close to the steep and subsequently slipped.
To the south of the Royal Enclosure lies a ring-fort known as Ráith Laoghaire (Laoghaire's Fort), where the eponymous king is said to have been buried in an upright position. Half a mile south of the Hill of Tara is another hill fort known as Rath Maeve, the fort of either the legendary queen Medb, who is more usually associated with Connacht, or the less well known legendary figure of Medb Lethderg, who is associated with Tara.
The most familiar role played by the Hill of Tara in Irish history is as the seat of the kings of Ireland until the 6th century. This role extended until the 12th century, albeit without its earlier splendor. Regardless, the significance of the Hill of Tara predates Celtic times, although it has not been shown that Tara was continuously important from the Neolithic to the 12th century. The central part of the site could not have housed a large permanent retinue, suggesting that it was used as an occasional meeting place. There were no large defensive works. Certainly the earliest records attest that high kings were inaugurated there, and the "Seanchas Mor" legal text (written down after 600AD) specified that they had to drink ale and symbolically marry the goddess Maeve (Medb) to acquire the high-kingship.
Previous scholarly dispute over Tara's initial importance advanced as archaeologists identified pre-Celtic monuments and buildings dating back to the Neolithic period around 5,000 years ago. One of these structures, the Mound of the Hostages, has a short passage which is aligned with sunset on the true astronomical cross-quarter days of November 8 and February 4, the ancient Celtic festivals of Samhain and Imbolc. The mound's passage is shorter than the long entryways of monuments like Newgrange, which makes it less precise in providing alignments with the Sun; still, Martin Brennan, in The Stones of Time, states that the daily changes in the position of a 13-foot (4-m) long sunbeam are more than adequate to determine specific dates.
A theory that may predate the Hill of Tara's splendor before Celtic times is the legendary story naming the Hill of Tara as the capital of the Tuatha Dé Danann, pre-Celtic dwellers of Ireland. When the Celts established a seat in the hill, the hill became the place from which the kings of Mide ruled Ireland. Although there is much debate among historians as to how far the King's influence spread; it may have been as little as the middle of Ireland, it may have been all the northern half. The high kingship of the whole island was only established to an effective degree by Máel Sechnaill mac Máele Ruanaid (Malachy I). Irish pseudohistorians of the Middle Ages made it stretch back into prehistoric times. Atop the hill stands a stone pillar that was the Irish Lia Fáil (Stone of Destiny) on which the High Kings of Ireland were crowned; legends suggest that the stone was required to roar three times if the chosen one was a true king (compare with the Scottish Lia Fail). Both the Hill of Tara as a hill and as a capital seems to have political and religious influence, which diminished since St. Patrick's time.
At one time, it was a capital offense to make a fire within sight of Tara.
During the rebellion of 1798, United Irishmen formed a camp on the hill but were attacked and defeated by British troops on 26 May 1798 and the Lia Fáil was moved to mark the graves of the 400 rebels who died on the hill that day. In 1843, the Irish Member of Parliament Daniel O'Connell hosted a peaceful political demonstration on Hill of Tara in favour of repeal of the Act of Union which drew over 750,000 people, which indicates the enduring importance of the Hill of Tara.
During the turn of the 20th century the Hill of Tara was excavated by British Israelists who thought that the Irish were part of the Lost Tribes of Israel and that the hill contained the Ark of the Covenant.
The Hill of Tara was included in the World Monuments Fund's 2008 Watch List of the 100 Most Endangered Sites in the world.
There is currently a letter writing campaign being undertaken to preserve the Hill of Tara.