No matter what your reason to come down to the southwest of the island, either for the resorts, or Beqa shark diving (highly recommended as one of THE top dives you will ever do in your life) or on your way to the east, you will pass the dunes on the lone road going around the island.
Even though the main attraction is the natural aspect of the park, the sand dunes, the place actually wants to be inscribed for the cultural relics found here. At first it didn't seem like there is much but I've seen sites inscribed for less. The site inside the park is off-limits and you can only enjoy the sand dune hikes. The hikes are pretty good though. It starts with hikes through lowgrass fields and eventually turns into tall dunes at the side of the beach, deep drop off and excellent views. By that time I had already lost the path though as I think it's not clearly signed once you get to the dunes. What's worse is that it started a downpour right as I reached the top and that can be pretty harsh in the Pacific islands.
After reaching the beach I finally found the signs again and could return to the museum. After it rained you don't really want to hike this park but you can just wait a couple of hours of sunshine and it's all good again. My visit was in March 2018 and they were just about the open up a better museum for the cultural aspect. I got a quick peek thanks to the friendly staff and I assume by now they actually opened it up so you can learn more about the park aside from "it's got dunes".
Recommended and only takes a few hours to visit thoroughly.