Known as the Garden Isle, Kauai is the fourth largest island in the Hawaiian archipelago measuring in at 562.3 square miles. It is also the oldest of Hawaii’s eight main islands and is full of incredible sites to behold — including one incredible fossil cave you might not be familiar with. The gorgeous Makauwahi Cave, an expansive cave and sinkhole, is often considered to be one of the Pacific’s richest fossil sites. In fact, many of the oldest and most diverse fossils in Hawaii can be found here.

Want to see this magnificent wonder for yourself? Near the end of the two-mile Mahaulepu Heritage Trail that begins at Shipwreck’s Beach on Kauai’s southern shore is a short path through the trees that leads to an often overlooked opening in the rocks.

Many tourists turn around at this point, but if you’ve done your research, you will get down on your knees and crawl through the crevice. Here, you will find yourself inside a cramped chamber that gives way to a jaw-dropping, lush natural amphitheater of sorts. This is Makauwahi Cave, not only the largest limestone cave in Hawaii but one of the state’s largest archaeological sites.

This relatively unknown archaeological site was formed when the once fossilized sand dune collapsed, though it wasn’t until 25 years ago that the cave was discovered as an archaeological site. The accessible portion of the cave was formed over the course of 400,000 years, and was once the site of a freshwater lake.

During their search for Hawaiian fossil sites on Kauai’s southern shore, four archaeologists discovered the cave’s access sinkhole in 1992, though the cave was known historically by Kauai residents and was known to be an ancient Hawaiian burial site.

The name Makauwahi — which translates to "smoke eye" in Hawaiian — was rediscovered by a local archaeologist in 2000 when he found reference to the cave in an essay written by a high school student more than a century prior.

The sinkhole has preserved records of floods, droughts, hurricanes, a massive tsunami, the pollen of now extinct native plant species, in addition to countless bones. The Makauwahi Cave Reserve website states that, "the rich fossil-bearing sediments of the Makauwahi Cave, over 33 feet thick in some areas, have an unusual chemistry that preserves almost everything that fell in there over the last 10,000 years or more."

The result? Some of the most pristine, archaeologically complete, and fascinating sets of fossils found in Hawaii ever.

The fossils found at this site not only document the conditions of this area before human colonization, but also the millennium of human occupation, including the drastic ecological changes that occurred since the first Polynesians (and later Europeans and Asians) settled in Hawaii, bringing with them a plethora of invasive alien species.

Bones found in the cave include those of various extinct animals, including some 40 species of birds, half of which are now extinct. You might also catch a glimpse of one of the cave’s living residents: this geological wonder is home to several giant tortoises that roam the area, serving as natural lawnmowers for the site’s invasive species.

Free tours are offered by the reserve throughout the week, giving visitors a unique glimpse into Hawaiian history by showcasing various fossils and artifacts that have been unearthed in the last twenty-some years – including everything from early Hawaiian tools to shells and bones.

Pretty cool, if we do say so ourselves!

What are you waiting for? Plan your visit to this hidden archaeological gem today! Tours of the Makauwahi Cave are available on specific days of the week. For more information, visit their website.

Need more inspiration for the perfect Kauai vacation? Why not stroll through the nearby Allerton Garden, or take this incredible weekend road trip across our favorite Hawaiian Island? (Hint: It's Kauai.)