Giant's Causeway basalt columns sunset, Northern Ireland

Polygon patch

If you're a geometry buff looking for a break outdoors, we've found the place for you. Here at the Giant's Causeway, you'll find not only a great abundance of hexagons, but squares, octagons, pentagons and even a handful of heptagons. Numbering around 40,000 and arranged in tumbling terraces, the Causeway's polygonal shapes showcase the signature columnar jointing of some types of igneous rock—in this case basalt. As lava flows cooled to form this rocky coast 60 million years ago, stress fractures followed the shortest distance between two points to create tight, uniform shapes. It's a pattern found all over the world, but this Northern Ireland landmark is probably the best-known example, drawing about a million visitors a year.