Stop #15:
Giants Causeway has over 40,000 basalt columns formed from ancient volcanic activity. Located on the northern coast of Northern Ireland, The causeway is a UNESCO world heritage site since 1986.
By legend, the stones are the remnants of a causeway built by a giant named Finn MacCool to connect giants destroyed the causeway (depending on which version of the story is told), leaving only the remnants of the causeway you see today.