A short walk into Skaftafell National Park in South Iceland provides visitors with a breathtaking view of Svartifoss (Black Falls). Ice-cold meltwater from the Svinafellsjokull glacier feeds the famous Svartifoss waterfall. The waterfall tumbles down 20 metres (80ft) over a cliff which is bordered on both sides by tall black basalt columns, resembling pipes of a giant organ, which is where the waterfall gets its name.
This wonder of natural architecture inspired the design for Iceland’s National Theatre and the Hallgrimskirkja church in Reykjavik. The hexagonal columns form inside a lava flow which then cools extremely slowly, giving rise to crystallization. Similar well-known lava formations are seen at the Giant’s Causeway in Northern Ireland, and on the island of Staffa in Scotland.
https://www.icelandtravel.is/attractions/svartifoss-waterfall/