Co Antrim&#x27;s Giant’s Causeway is a true world wonder Made up of 40,000 black basalt columns jutting from the sea on Northern Ireland&#x27;s Antrim plateau, the site, featured in many local legends, has been studied extensively by geologists. Formed through volcanic activity during the Tertiary period, 50-60 million years ago, it was declared a World Heritage Site in 1986.