Reynisfjara, just west of Vik, is Iceland's most celebrated black sand beach and with good reason. The combination of jet-black basalt sand, towering hexagonal rock columns, and dramatic sea stacks offshore makes it visually unlike anywhere else in the country. On overcast days — which is most of them — the mood is appropriately gothic. On rare clear days the contrast of black sand, white surf, and blue sky is genuinely extraordinary.
The beach has a justified reputation for danger. The waves here are North Atlantic swells that have built up across thousands of miles of open water; they arrive fast, hit hard, and run up the beach with almost no warning. People are killed here regularly by what are called sneaker waves. The advice is blunt: stay well back from the waterline, never turn your back on the surf, and watch the water pattern carefully before going anywhere near it. The cave and basalt columns at the western end of the beach are accessible when conditions are calm, but never attempt to explore the cave if there is significant surf. The small visitor centre near the car park has safety information.