Most of Ireland’s big dolmens sit out in fields at the end of a walk. This one is in a garden. Aideen’s Grave is a Neolithic portal tomb in the grounds of Howth Castle, dating to around 2500 BC, and it is the second-largest of its kind in the country, behind only the Brownshill Dolmen in County Carlow. You reach it on the castle’s garden paths rather than a hillside scramble, which makes it one of the more accessible prehistoric monuments near Dublin.
The stones
The capstone is the thing. It measures roughly 5 metres long, 4 metres wide and 2 metres deep, and is estimated at 68 to 75 tons. Over the centuries it has slipped backwards and now rests on the upper edges of the two portal stones, each about 2.5 metres high, hanging above the collapsed chamber. The original doorstone has fallen.
Stand back a little and the scale lands better than it does up close. It is worth remembering how the thing was built: levered into place with wooden rollers, ropes and a great many people, with no metal tools and no wheels.
The legend of Aideen and Oscar
The name comes from a legend popularised in the 19th century by the poet and antiquarian Sir Samuel Ferguson. In the tale, Aideen is daughter of Aenghus, ruler of Howth (in Irish Beann Éadair), and marries Oscar, a warrior and grandson of Fionn McCool. When Oscar is killed at the Battle of Gabhra, around 284 AD, Aideen dies of grief, and the poet-warrior Oisín buries her on Howth Head under the tomb.
Worth being honest about: this is a Victorian literary invention, not an ancient oral tradition, and scholars treat it as such. The monument predates the story by thousands of years. A more local folk version has Fionn McCool flinging the stones over from the Bog of Allen in County Kildare during a game of pitch-and-toss with a rival giant.
Visiting the dolmen
Follow the main garden paths from the Howth Castle entrance. The route runs through maintained grounds, easing the jump between the medieval castle ruins and the prehistoric tomb. In late spring and early summer the rhododendrons and azaleas are in full colour, though that same foliage can partly hide the dolmen; a walk around the perimeter finds the clearer angles.
The elevated position opens out across the bay. On a clear day you can pick out Lambay Island, Ireland’s Eye, the city skyline and, further off, the Wicklow Mountains.
Practical information
| Item | Details |
|---|---|
| Location | Howth Castle Gardens, Howth Head, Co. Dublin |
| Opening hours | Gardens daily 09:00-18:00 (seasonal variation). The dolmen is free and accessible year-round. |
| Admission | Free to the dolmen and gardens. Castle interior tours are suspended during restoration. |
| Accessibility | Main paths are largely level and paved. The final approach has uneven ground and low stone steps, awkward for standard wheelchairs or pushchairs. |
| Getting there | DART to Howth station (about 30 minutes from the city centre), then walk or cycle to the castle entrance. By car, follow the R105 to Howth and use the estate parking near Deer Park Golf. |
| Facilities | Café, toilets and a gift shop within the castle grounds. |
| Website | https://howthcastle.ie |
Nearby
- Howth Castle Gardens – Terraced grounds with a 32-foot beech hedge planted in 1710 and over 200 species of flowering shrub.
- National Transport Museum of Ireland – In the former Mariners Church, with vintage trams, buses and a 10-ton revolving lighthouse lens.
- Corr Castle Ruins – A 16th-century tower house on the peninsula.
- Howth coastal walks – Cliff trails out of the village; the Black Linn Loop gives the sea views and passes the Bailey Lighthouse.
Allow about 45 minutes for the dolmen and the gardens. Parking fills on weekends, so arrive before 10.30am or take the DART. If you are continuing onto the cliff paths afterwards, check the tide times first, as some sections can be cut off in high tide or rough weather.