The United States is home to more than 400 national parks and travelers will have numerous opportunities to explore them during National Park Week 2022, which runs April 16-24, kicking off with a rare free entrance day on Saturday, April 16. While many will flock to iconic and popular protected lands like the Grand Canyon, Smoky Mountains, Yosemite and Yellowstone, others will be lucky enough to discover some of the nation's hidden gems. Whether it's peering beneath the ocean's surface to uncover thousands of years' worth of history or gazing into one of the darkest night skies on the planet, there are a handful of underrated national parks worth exploring this spring.

Overshadowed by bustling Miami just across the bay, Biscayne National Park is easy to forget about considering that it's made up of 95 percent water. However, this South Florida gem rewards visitors with some of the world's most beautiful coral reefs, majestic islands, and see-through waters as well as a whopping 10,000 years of human history going back to days before rising sea levels.

While Yosemite and Joshua Tree tend to get lots of love, Northern California's Lassen Volcanic National Park shouldn't be overlooked. This diverse landscape is one of the best for stargazing, no doubt, but also boasts a series of can't-miss natural attractions, including volcanoes, steaming fumaroles, wildflower-filled meadows and pristine lakes.

Arizona's Grand Canyon and Saguaro National Parks are undoubtedly worthwhile trips for visitors to the Southwest but the same can certainly be said for Petrified Forest National Park in the northeast portion of the state just off of I-40. Visitors can conveniently experience many of the highlights of this protected land from the comfort of their vehicle but will want to pull over to explore the Painted Desert and the park's namesake petrified logs dating back millions of years.

2022 marks the 100th Anniversary of the designation of Lehman Caves National Monument, which is now a part of Nevada's Great Basin National Park. In addition to stalactites, stalagmites, cave shields and other natural wonders, visitors can hike through ancient bristlecone pines, conquer the 13,000-plus-foot Wheeler Peak and gaze up at one of the darkest night skies in what's been designated an International Dark Sky Park.

Located a little more than two hours from Seattle just south of the U.S.-Canada border, North Cascades National Park is a picturesque locale boasting some of the best hiking in the Pacific Northwest. After all, the park is home to more than 400 miles of trails, many of which offer gorgeous views of glacier-capped peaks, forested valleys, lakes, creeks and wildlife.

The very first cave to be designated a national park anywhere in the world can be found in western South Dakota. Wind Cave National Park protects one of the longest and most complex caves in the world and is home to the extremely rare honeycomb-like boxwork calcite formation. Outside of the cave, visitors can experience bison, elk and other wildlife on the largest remaining natural mixed-grass prairie in the U.S.

Travelers with a passion for kayaking and canoeing will want to put northern Minnesota's Voyageurs National Park at the top of their bucket list. Offering a whopping 218,055 acres of both land and sea to explore, this destination knows no boundaries and features not only some of the oldest rocks on the continent of North America but one of the best viewpoints of the northern lights in America.

You'll find the deepest lake in the U.S. (1,950 feet) at Crater Lake National Park in southern Oregon. Celebrated for its deep blue color and clarity courtesy of rain and melted snow, this lake and surrounding park are ideal for scenic hiking, biking, fishing and camping. The collapse of Mount Mazama may have occurred 7,700 years ago but visitors can still appreciate its wonder in 2022.

The only national park named directly after a single person, Theodore Roosevelt National Park in western North Dakota honors the passion of the 26th President of the U.S., who first came to the Dakota Territory in 1883 to hunt bison. One of three sections, the Elkhorn Ranch Unit of the park preserves Roosevelt's former home, where only the cabin's foundation stones remain. However, visitors will also discover an abundance of scenery and wildlife as they navigate dozens of miles of roads and trails.