Rath of the Synods


The Rath of the Synods is named in an 11th-century text to commemorate ecclesiastical synods reputed to have been held at Tara by important Irish saints such as Adomnán, abbot of Iona (died 704) and Brendan. Large parts of the site were destroyed between 1899 and 1902 by the British Israelites whose researches led them to believe that the Ark of the Covenant had been buried there. Scientific excavations were carried out on the site by Professor Seán P. Ó Riordáin in 1952 and 1955 and four major phases of activity were identified.

During the first phase the site was a cemetery consisting of an oval-shaped enclosure (27.5m by 32m) defined simply by a ditch and a small ring-barrow to the northwest, now tucked between the middle and outer ramparts.  In its original form the barrow (about 17m in diameter) consisted of a cairn of stones covered by a mantle of soil thrown up from the excavation of the ditch. There were five primary cremation burials in the mound. Later, however, the top of the mound was levelled and spread out, thus creating a wider but slighter monument. Five burials are associated with this phase, four cremations and one crouched inhumation which was placed over the centre of the mound. There were no associated artefacts and the time interval between the two stages cannot be ascertained.

The second phase is characterised by a series of palisaded enclosures ranging in diameter from about 16m to about 30m. At least four distinct building episodes are attested, including the erection of at least one circle of free-standing wooden posts. The design and layout of these structures compare well with ritual and high status buildings at Dún Ailinne and Eamhain Mhacha which have been dated by excavation to the Iron Age and this suggests that they share a common, ceremonial purpose. A layer of sterile yellow soil seals these deposits and marks the end of this phase of activity.

During the third phase the site was once again used as a cemetery. We do not know if the area was formally defined, but there was a cluster of seven burials consisting of five inhumations and just two cremations. The proportionately greater number of inhumations reflects a gradual change in the burial rite from cremation to inhumation that took place during the first few centuries AD.

The building of an enclosure (83m in diameter) represents the fourth phase of activity. It is one of the very rare examples with four sets of ramparts. Others include Tlachtga on the Hill of Ward, a little to the west of Tara, and Rathra near Crúachain, County Roscommon. Like the Rath of the Synods, these too surround earlier burial mounds and it is clear that between them they constitute a special class of ritual or ceremonial monuments. The inner enclosure appears to have been aligned on the phase one ditched enclosure and the enclosure was positioned so as to facilitate the incorporation of the ring-barrow between the outer two ramparts. Each rampart consists of a bank and external ditch which, though substantially silted over today, originally attained depths of between 1.5 and 2m. The inner faces of the outer two banks may have been timber-faced. Remains of two rectangular buildings were found in the interior and the range of associated artefacts suggest that the site was in use during the period 500 BC – 500 AD. Direct contact with the Roman world (probably Roman Britain) is also evidenced in the assemblage which includes objects such as a lead seal, a layered glass inset for a ring or brooch and an iron barrel padlock.




Technical Details

Monument Type: Enclosure SMR Record: ME031-033016-

FLI-MAP 400; an aerial LiDAR survey system, was initially designed to survey infrastructural assets such as roads, railways and electricity supply networks. The sensor system mounted beneath the main helicopter fuselage consists of:

  • FLI-MAP 400; an aerial LiDAR survey system, was initially designed to survey infrastructural assets such as roads, railways and electricity supply networks. The sensor system mounted beneath the main helicopter fuselage consists of:
  • Three 150 kHz LiDAR sensors (7◦ forward, nadir and 7◦ aft);
  • Scanning angle 60◦
  • Accuracy (relative) Horizontal 5 cm, Vertical 3 cm
  • Multiple returns 4
  • Two RTK GPS receivers – provide accurate location in used in conjunction with RTK base stations;
  • Inertial Navigation System (INS)- continuously track the position, orientation, and velocity of the helicopter;
  • Digital imaging (11 megapixel) and digital video capture

Resulting data sets include first return (DSM) and last return point (DTM, bare earth) models

Post-processing was completed in Geomagic Studio 2012 software: individual scans are edited, aligned, before a final surface is generated using global registration, fusion, and a small objects filter algorithm.. For dissemination purposes a 3D version of the model was generated using simplification, retopologisation and texturing processes utilising Autodesk Mudbox and 3DS Max.

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