Giant's Causeway: Northern Ireland's Stone Stepping Stones

What is the Giant's Causeway?

The Giant's Causeway is a coastal area of about 40,000 tightly fitted stone columns ¹. It sits in County Antrim, in Causeway Coast and Glens, on the north coast of Northern Ireland ¹². The country is the United Kingdom ².

Most columns have six sides, but some have four to eight sides ¹. The tallest stand about 12 metres high ¹. Their flat tops form natural stepping stones that run from the base of the cliffs and slip under the sea ¹.

The site is protected as a World Heritage Site and as a national nature reserve ¹². Much of it is cared for by the National Trust, while other parts belong to the Crown Estate and private owners ¹.

How did the columns form?

About 50 to 60 million years ago, during a time called the Paleocene Epoch, this part of Antrim saw strong volcanic activity ¹. Very runny melted rock, called basalt, pushed through chalk beds and spread into a wide volcanic plateau ¹.

As the lava cooled, it shrank ¹. The shrinking made cracks, much like cracks in drying mud ¹. The cracks spread downward and left tall pillar shapes ¹. Later breaks across the pillars made shorter sections, sometimes called biscuits ¹.

Many joints fit together as ball and socket shapes, with a rounded bottom and a hollow top ¹. The speed of cooling largely set how wide each column grew ¹. These rocks were once part of a large volcanic area called the Thulean Plateau ¹.

Why is it special, and what should visitors know?

Scientists value the site because it helped people understand volcanoes and basalt ¹. In 2022, it was listed among 100 geological heritage sites around the world ¹. Readers have also voted it among the top natural wonders in the United Kingdom ¹.

Stories add another layer ¹. Legend says the Irish hero Fionn mac Cumhaill built a causeway to face the Scottish giant Benandonner ¹. In one tale, Fionn wins. In another, his wife hides him as a baby to frighten Benandonner away ¹. Matching columns stand across the sea at Fingal's Cave on Staffa, and they come from the same ancient lava flow ¹.

The place draws many people, with nearly one million visitors in 2019 ¹. Entry to the stones themselves is free, and visitors do not have to go through the paid visitor centre ¹. As of October 2026, check the National Trust for current paths, safety advice and facilities before you go.