The Giant's Causeway is a headland on the north coast of Northern Ireland where some forty thousand columns of black basalt, most of them hexagons, step down out of the cliffs into the Atlantic, fitted together so neatly that they look laid by hand. They were made by cooling. Around sixty million years ago lava flooded this coast and hardened slowly from the top down, shrinking as it cooled and cracking into columns the way drying mud cracks into plates; the pattern is six-sided because that is how shrinking rock most evenly splits, though some columns have four, five, seven or even eight sides. The tops are worn flat, and you walk out across them from column to column down the great apron where it slopes into the sea, the waves breaking over the lowest stones. Among the thousands, generations of visitors have found shapes and named them: the Giant's Boot, the Organ, the Wishing Chair, the Camel.
The legend is older than the science. Finn McCool, the Irish giant, built the causeway across the sea to fight the Scottish giant Benandonner, then saw how big his rival really was and fled home, and the road was torn up behind him; the matching columns at Fingal's Cave on the Scottish island of Staffa are, in the story, the other end. For a long time scholars argued about the columns too, some insisting the sea had built them, others that they had grown like crystals, until the volcanic answer won. The cliff path above the stones gives the view the shore hides: from up there the whole formation reads as a single honeycomb sheet ringed by an amphitheatre of taller columns. From spring into summer fulmars, kittiwakes and guillemots nest on the ledges above, and black guillemots bob in the coves at the foot. The last hour before dark, once the coaches have pulled away, is when the stones go copper and the shore empties, and the causeway looks most like what the story says it is.