Giant's Causeway

Portcoon Cave

Useful Information

Location: Bushmills.
On the Causeway Coast between Causeway Head and Benbane Head, on the north coast of County Antrim, Northern Ireland.
(55.233433, -6.516904)
Open: no restrictions.
Fee: free.
Parking: Car GBP 5.
Classification: Tertiary lavas of the Antrim Plateau. Sea caves.
Light: LightIncandescent Electric Light System
Dimension: Average height of the cliffs: 100m
Lava flow covers 3,800 km²
Number of columns: approx. 40,000
Size of columns: 45 cm in diameter (average)
Guided tours:  
Bibliography: H.E. Wilson and P.I. Manning (1978): Geology of the Causeway Coast, Geological Survey of Northern Ireland. Two volumes. HMSO
P.S. Watson (1992): The Giant's Causeway - A Remnant of Chaos, HMSO.
Address: National Trust, North Coast Office, Giant's Causeway, 42 Causeway Road, Bushmills, Co. Antrim.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1771 Desmarest concluded, the Causeway was a lava flow.
1786 Hamilton produced the first detailed analysis.
1887 the first hydro-electric tramway (built 1883) was extended to the Causeway Head. Two hotels and numbers of guesthouses were built.
1961 bequeathed to the National Trust by Sir McNaghten.
1940 scientific work by Tomkeieff.
1955 scientific work by Patterson.
1986 inscribed on the UNESCO World Heritage List. Visitor center opened.


The Giant's Causeway is a mass of basalt columns at the northern coast of Ireland. It has been designated a world heritage site by UNESCO. But it is not really subterranean, so it would normally not be included into There are two reasons, why we included it anyway:

  1. Giant's Causeway is the most impressive geological sight in Ireland.
  2. On the walk to Portbraddan lie several sea caves with remains of Stone Age.

From the Giant's Causeway Centre you can take the low road to the Grand Causeway and on, past strange rock formations to Port na Spaniagh where the Armada treasure ship Girona sank in 1588. Then up Benbane Head via the wooden staircase. From here you can return along the cliff top. The specific sites of interest are:

To visit the caves you will have to do some walking. Start in Portbraddan, which has Ireland's tiniest church. At the East end the track passes between islets of Carricknaford and the old shoreline of a raised beach. Here are some sea caves, where stone age flints have been found.

Probably the most visited cave is Portcoon Cave. It is entered from the back until the shore is reached. About 10 to 15 m high and 150 m long it resembles a narrow tunnel. This cave was visited and published since Victorian times. There are 19th century engravings and old postcards showing this cave, and many references of travelers describing the cave. However, it seems the place is not featured any more and visitors have to know about it to find it.