Mammoth Cave is the superlative superstar of the Bluegrass, earning the state worldwide acclaim and attention. Visiting Mammoth Cave is a bucket list must. The cavern system features over 400 miles of underground caverns and passageways, with more miles frequently added. In addition to its epic underground tours, aboveground adventures abound at Mammoth Cave, too. The trails are spectacular, and the national park is, pardon the pun, a stellar place for stargazing. Oh, and did we mention it's extraordinarily beautiful? Check out these Mammoth Cave photos and you'll agree!

Within the rolling hills of west-central Kentucky, nestled on the edge of America's Southern Appalachian Region, lies an underground world millions of years in the making.

This is, of course, Kentucky's Mammoth Cave National Park, the longest and most well-known cave system in the world.

A United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site and Biosphere Reserve, this sandstone labyrinth encompasses more than 400 miles of known passageways, with more being discovered all the time. Visiting Mammoth Cave is something you should definitely do more than once.

Over two million people visit Mammoth Cave each year to revel in this otherworldly underworld. Tours led by rangers at Mammoth Cave National Park range from short, well-marked routes to extensive off-trail forays into the depths of this vast network of passages. But no matter which you choose, Mammoth Cave photos are a must.

The Violet City Lantern Tour is a fan favorite when it comes to Mammoth Cave tours. This three-hour tour covers three miles -- all by lantern light! This tour offers an in-depth look at Mammoth Cave's rich history and most intriguing geological features.

One of the most interesting (and difficult) areas we traversed came on the Historic tour.

It was a tight squeeze, but I put aside my claustrophobia and got through!

Play around with the settings on your camera while you're underground and you'll get some truly amazing Mammoth Cave photos.

I was really amazed at some of my shots!

And the various "rooms" within Mammoth Cave will drop your jaw. This, for example, is the Frozen Niagara. This large formation can be seen on the Domes and Dripstones, Frozen Niagara, Grand Avenue, Introduction to Caving, and Wild Cave tours. My favorite while visiting Mammoth Cave was definitely Domes and Dripstones.

But Mammoth Cave is anything but a one-trick pony (or horse, because, Kentucky); above-ground adventures abound at this national park. The lushly forested park above the caves boasts hiking and equestrian trails, plus canoeing, kayaking, and some pretty amazing waterfall chasing! And of course, there are plenty of opportunities for Mammoth Cave photos.

And when the sun sets over Mammoth Cave National Park, the real aboveground show begins.

Recently designated an official Dark Sky Park, Mammoth Cave National Park is both a National Park Service-operated site *and* Dark Sky Park. The stargazing here is nothing short of extraordinary, so definitely plan on visiting Mammoth Cave at night if you can.

There's also some stuff to see outside!

I am a sucker for trains, so I was super interested to see these steam engines that began running more than a century ago.

From above and below ground, to all corners, nooks, and crannies of this national park, everything about Mammoth Cave is spectacular... and spectacularly beautiful, too. Be sure to head out on a Mammoth Cave tour and/or explore on your own!

Get more details about Mammoth Cave tours.

Need some new hiking gear before visiting Mammoth Cave? Check out what Backcountry has to offer.

When was the last time you explored Kentucky's world-famous national park? Not only is Mammoth Cave an epic bucket list accomplishment, but it really is the most beautiful place in Kentucky. Share your experiences here in the comments below!

Looking for some more scenery in the Bluegrass State? Check out the best hikes in Kentucky.