Seahan straddles the boundary between the counties of Wicklow and Dublin. The underlying granite bedrock of the mountain was formed during the Devonian Period between 415 and 360 million years ago. The mountain stands some 647m (2,123 feet) high, making it one of the tallest of the Dublin Mountains.



The tombs on the summit of the mountain were constructed in the Neolithic Period, probably around 3,500–3,300 BC. They originally consisted of a large cairn of stone that covered a burial chamber that was accessed by a passageway. Here you can see that one of the tombs has had its stone cairn removed, allowing you to see its passageway and burial chamber. This may have been removed during informal antiquarian excavation in the nineteenth century, though no record of such an excavation has been recorded. An alternative explanation could be that the stones may have been quarried in antiquity to construct the cairn of the the larger tomb that is now topped by the Ordnance Survey Trigonometry Pillar. Perhaps this was done as a conscious act, to slight the older tomb and those interred within, in favour of the new tomb that may have been built by a different community.



The tombs on the summit of Seahan are some of the most important of the Dublin Mountains. These tombs are part of an extended cemetery of passage tombs that crown the summits of a number of the other mountains in Dublin and Wicklow. Inter-visibility of the tombs appears to have been an important feature to the Neolithic builders, and from here you can clearly see the tombs on the summit of Seefin and Seefinghan to the south.

The whole area is soaked in ancient myths and legends. Fionn Mac Cumhaill and the Fianna are associated with both the nearby valley of Glenasmole to the north-east of Seahan, and with Seefin (Suí Finn – Finn’s Seat) to the south. It is said that one of Fionn’s favourite pastimes was to hunt deer in the valley of Glenasmole, before returning to Seefin to feast. Once Fionn and the Fianna were out hunting in pursuit of a large stag in Glenasmole. They came upon three beautiful women who offered them food and drink. Tired and thirsty after a long hunt on a hot day, Fionn and his men gratefully accepted. Though as soon as they drank from the cups they fell into paralysis, and though they could see and speak they could not move. The three women brought spears and swords, and stood in front of the immobile Fianna and declared that “We have heard of Fionn the Mighty, and it is the wish of our Queen that he should be her husband”. However one of the three beautiful women had also taken an interest in one of the Fianna, a handsome young warrior named Diarmid. He was known as ‘Diarmid of the love spot’, and it was said that no woman could shield her heart from him. She moved closer to him, and as she did, found that she could not resist kissing him. As soon as they kissed, the spell was broken, and the beautiful young women turned into withered old witches. Fionn and the other Fianna quickly killed the three witches and fled the valley.

Text and Photos: Abarta Heritage

Useful Resources

National Monuments Service

NMS Historic Environment Viewer

South Dublin Libraries Local Studies Resources

South Dublin Historical Mapping

South Dublin County History

South Dublin Libraries SOURCE  - a digital archive of local studies material relating to South Dublin County


[last updated: 24.07.20]

Archaeology Sites in the Dublin Mountains

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