Wiki – “Some 50/60 million years ago, during the Paleogene period, Antrim was subject to intense volcanic activity, when highly fluid molten basalt intruded through chalk beds to form an extensive lava plateau. As the lava cooled rapidly, contraction occurred. Horizontal contraction fractured in a similar way to drying mud, with the cracks propagating down as the mass cooled, leaving pillarlike structures, which are also fractured horizontally into "biscuits"”
First, I was surprised by how small the individual pillars were, somehow I was expecting giant stepping stones. Secondly I was amazed at how many of them there where, and then finally, sitting up on one of the highest rocks, how small the whole area was.