It’s getting harder and harder to find unique spots in the world. Cities all have similar stores and restaurants. Hotel chains dominate beach and mountain resorts. The same brands even greet you at new airports. So you now turn to nature to find things that are uncommon. Macquarie Island is as rare as it gets.

Upon first glance, Macca is just another subantarctic island. An Australian discovered the craggy island, located halfway between New Zealand and Antarctica, in 1810 when searching for new seal-hunting grounds. The 49-square-mile island was claimed for Britain, annexed by New South Wales, and ultimately administered by Tasmania. It’s been home to the Macquarie Island Station, an Australian Antarctic Division research base, since 1948. Then it became a state reserve in 1978. UNESCO followed suit 20 years later.

Macca is also home to thousands of seals and millions of penguins. Three types of fur seals—Antarctic, subantarctic, and New Zealand—live here. Massive southern elephant seals do, too. The world’s entire population of royal penguins, with their yellow crests, descend on the island during nesting season. Long-tailed gentoo, king, and southern rockhopper penguins use the island, as well. Blue-eyed Macquarie shags call the island home year-round. While the surrounding frigid waters are where orcas and southern right whales live. They all make Macca impressive, but still not unique.

So what is it that makes this remote island so special? It’s the only place in the world where the earth’s mantle—the layer between the crust and the outer core—is exposed above sea level. Two tectonic plates met at an underwater ridge and pushed the ocean’s crust—a three-mile-wide portion of it—above the water. You can see the green stones, known as ophiolites, when you hike across the windy island.

Now you have penguins, seals, a fascinating research center, and the earth’s mantle all in one place. You can even buy an Australian Antarctic Territory stamp—a souvenir few people can claim—when you visit Macquarie Island. Extraordinary indeed.