Just a short walk from the car park at Reynisfjara Beach, you'll discover the incredible Hálsanefshellir Cave. The entrance is framed by massive, geometric basalt columns. Inside, the view of the Reynisdrangar sea stacks through the cave's mouth is something special. Be incredibly mindful of the ocean here; the waves are famously unpredictable and powerful, so you must only venture into the cave during low tide and never, ever turn your back on the water.