Hana no Iwaya is a shrine without the usual built-up shrine drama. Its focus is a towering sacred rock associated with Izanami, one of the creator deities in Japanese myth.
That older style of worship is the point. Rather than a grand hall or a bright gate, you stand below stone, rope, and trees, with the Pacific coast just beyond. It is part of the World Heritage story of the Kii Mountain pilgrimage landscape.