A UNESCO World Heritage Site, this is an extraordinary sight indeed. Sitting at the foot of steep cliffs and stretching out into the sea, it is a natural formation of thousands of tightly packed basalt columns. The tops of the columns form flat stepping stones, all of which are perfectly hexagonal. They measure about 30cm (12 in.) in diameter; some are very short, others are as tall as 12m (39 ft.). Scientists believe they were formed 60 or 70 million years ago by volcanic eruptions and cooling lava. The ancients, on the other hand, believed the rock formation to be the work of giants. To reach the causeway, you walk from the parking area down a steep path for nearly a mile (1.6km), past amphitheaters of stone columns and formations with fanciful names like Honeycomb, Wishing Well, Giant’s Granny, King and his Nobles, and Lover’s Leap. If you wish, you can then climb up a wooden staircase to Benbane Head to take in the views, and then walk back along the cliff top. Regular shuttle service from the visitor center is available for those who can’t face the hike. Note: The high-tech, underground visitor center has a cafe, shop, interpretive center, and hugely expensive parking, justifying the fairly steep admission price. However, the Causeway itself is a free, open site, so if you can find safe and legal parking, there’s nothing to stop you from walking down on your own.