Dolmen Hill of Tara Aligned with Celtic Sun Celebrations and a Lunar Standstill

August Schwerdfeger, CC BY 4.0 , via Wikimedia Commons

The Hill of Tara is a hillside attraction in Ireland with a Dolmen called Mound of the Hostages. It is believed to have been built around 3.200 BC and is the oldest structure on this hill. Martin Brennan has discovered that this dolmen is aligned to the Celtic Sun celebrations Samhain or better known as Halloween and Imbolc. As an Archaeoastronomer (An expensive word for someone who researches archaeological structures from an astronomical point of view, so Sun, Moon and Stars), I have also investigated the alignment of the Mound of the Hostages dolmen, resulting in a remarkable discovery. This dolmen seems to have a double alignment on Sun and Moon!  In this article I’m going to try to explain how I see it.

Let’s take the ground plan of the dolmen, see drawing Mound of the Hostages. At the back of the corridor from this dolmen is a huge stone, which can be divided imaginary into two halves. When the Sun rises during Samhain or Halloween, at the beginning of the Celtic Winter and New Year, it shines right on the left half of this stone. This always happens on the way to Mid. Winter. On the way back from Mid. Winter the Sun again shines on the left half of this stone to indicate that Imbolc, the Celtic Spring, has begun. The right half of the huge stone at the back of the corridor is shined by the rising Moon during the Minor Lunar Standstill. This position is occupied by the Moon every 18,5 or 19 years for about a year. See my article or documentary about Stonehenge¹ for more information about Lunar Standstills. I really love how the builders of Mound of the Hostages with so much ingenuity, knowledge and precision managed to capture Sun and Moon in one construction some 5.000 years ago. I really admire this! So, the people of the Stone Age were not that primitive at all.

For the Dolmen Builders, the Sun position that the Celts call Samhain/Imbolc is rather important, because as a Dutchman I have discovered that most dolmens in the Netherlands are also aligned in this direction of Sunrise or Sunset². The same applies to a dolmen in Carnac (Dolmen de Kercado) in France Brittany.

For the Celts, Samhain (that we know as Halloween), was one of their most important annual celebrations. They celebrated the start of the Celtic New Year and the beginning of Winter. Currently this festival starts on October 31 and lasts three days, but before the Roman calendar was introduced this was probably October 26, because the Sun then rises exactly by 110°, halfway Mid. Autumn (the Celtic Mabon at 90°) and Mid. Winter (the Celtic Joel or Yule at 130°). According to the Celts, at that moment the veil between the spiritual and physical world is the thinnest. So, it’s the right time to connect with deceased ancestors and honor them. Would this Solar celebration therefore have been so important for the Dolmen Builders?

Mound of the Hostages was extensively researched in the 1950s by Sean P. Riordain and Ruaidhri de Valera³. This revealed that in this small burial mound with dolmen of about 40 meters in section, the remains of more than 300 people were added over a period of about 1.500 years (3.200 – 1.700 BC). So that’s a lot of ancestors together. Therefore, I believe this was a place to make contact with ancestors and honor them here with a celebration or consult. The Moon also seems to play an important role in honoring ancestors, because besides dolmen Mound of the Hostages are a number of Dutch dolmens also oriented towards the Moon. Additionally, Stonehenge has more clues for a Moon Temple¹ than for a Sun Temple and there are hundreds of burial mounds around the complex. In this way Stonehenge seems to be the center, with Moon orientation, of a huge cemetery and thus a place to honor ancestors.

In this article I connect the Dolmen Builders with the Celts, but there are thousands of years of time difference between the two cultures. How is that to rhyme?  In this, the Hill of Tara comes to help me out. This special place was from the Dolmen Builders (3.200 BC) always been in use until the early Middle Ages (500 AD) and therefore also in the time of the Celts.

After the construction of Mound of the Hostages by the Dolmen Builders in 3.200 BC, this mound was still in use over 1.500 years to bury people. About 2.000 BC the Bronze Age entered Ireland and burial mounds were built on the hill, see drawing Hill of Tara. The special thing about this is that the two burial mounds of The Sloping Graves along with the burial mound Gráinne’s Fort in the north seem to have the same alignment with the Sun (Samhain/Imbolc at 110°) as the much older dolmen on the hill. The Celts arrived around 600 BC in Ireland and brought the Iron Age to the island. They too built burial mounds and thus continued this tradition. In the Celtic period (600 BC to 500 AD) several burial mounds and/or earthworks were added to the Hill of Tara with the same alignments that can also be found in Mound of the Hostages. Looking at the burial mound Dall and the earthwork Raith of the Synods, with burial mound, both structures also seem to represent the same alignment with the Sun (Samhain/Imbolc at 110°) as recorded in the dolmen Mound of the Hostages. If we look at the alignment of the earthworks The Forrad and Cormac’s House, we find the same Moon alignment (Minor Lunar Standstill at 121°) as in the thousands of years older dolmen.

The ground plan of the Hill of Tara seems to indicate that important Sun and Moon alignments have always been in use from the Dolmen Builders, through the Burial Mound Culture, to the Celts. So, these celebrations do not descend from the Celts but seem to be thousands of years older.

Peter van den Hoek

Nieuwstraat 22 D

3811 JZ Amersfoort

The Netherlands






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