The Giant’s Causeway is around 40,000 interlocking basalt columns, mostly hexagonal, stepping down into the sea near Bushmills. It’s Northern Ireland’s only UNESCO World Heritage Site and the best-known stop on the Causeway Coastal Route — a straightforward drive from Ballymoney.
The geology
The columns formed roughly 50–60 million years ago, when intense volcanic activity in the area produced a lava plateau. As the thick basalt lava cooled slowly and evenly, it contracted and cracked into the columns you see today — the same process that produces mud-crack patterns on a much larger scale. Most columns are hexagonal, but you’ll find some with four, five, seven, or eight sides scattered through the formation.
The wider site includes named formations along the coastal path — the Giant’s Boot, the Wishing Chair, the Organ — worth the walk beyond the main causeway itself if you have the time.
The legend
According to Irish mythology, the causeway was built by the giant Fionn mac Cumhaill (Finn McCool), who was challenged by the Scottish giant Benandonner and built a stone path across the sea to reach him. The story is told inside the National Trust’s visitor centre, which opened in its current architecturally distinctive building in 2012.
How it became known
The Causeway had been known locally for centuries, but it entered wider scientific record after William King, Bishop of Derry, visited in 1692. A paper describing the site, based on an account from that visit, was presented to the Royal Society in London in 1693 — the formation’s first real introduction to a wider audience.
Visiting
- Location: near Bushmills, a short drive from Ballymoney via the Causeway Coastal Route.
- Access: the causeway itself is free to walk to and explore. The National Trust visitor centre charges for parking and the exhibition, though members and those on foot/bike/bus can often avoid the parking charge — check current National Trust pricing before you go.
- Footing: the basalt columns are uneven and can be slippery when wet or covered in sea spray — sturdy footwear is genuinely worth it, not just advice for the sake of it.