Editor's Note — CNN Travel has updated this story to mark National Park Week,
April 20-28, 2019. The National Park Service is offering free park admission on April 20 at those parks that charge a fee, as well as special programs and events throughout the week.
(CNN) — Yellowstone, Yosemite and the entire country of Switzerland would fit inside the United States' largest national park, a 13.2 million-acre expanse in Alaska.
And it would take about 2,400 of the smallest of the 61 headliner national parks to fill the biggest park's pristine, mountainous terrain.
Elsewhere in Alaska, climbing North America's tallest peak takes trained mountaineers two to four weeks, round trip, while visitors to the world's hottest spot -- which is also North America's lowest and driest spot -- are advised to "travel prepared to survive."
The world's longest contiguous cave system isn't yet completely explored, and it may never be.
All these wonders are protected within 419 national park sites spanning more than 84 million acres, all overseen by the US National Park Service in every state, the District of Columbia, American Samoa, Guam, Puerto Rico and the Virgin Islands.
CNN explored 10 record-setting spots, now protected because of legislation passed 100 years ago to preserve the nation's natural and cultural treasures for current and future generations.
1. Largest national park site
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Wrangell-St. Elias National Park & Preserve, Alaska
Yellowstone National Park, the world's first national park and a UNESCO World Heritage site, is enormous.
But the 2.2 million-acre Yellowstone doesn't even come close to the nation's largest national park, the remote Wrangell-St. Elias National Park & Preserve in Alaska.
It would take six Yellowstones to fill Wrangell-St. Elias' 13.2 million acres.
Wrangell-St. Elias is also home to the nation's largest glacial system, nine of the 16 highest US peaks, North America's largest piedmont glacier and longest tidewater glacier and the world's longest interior valley glacier.
More than 25% of Wrangell-St. Elias is covered by glaciers, which could explain why this park 200 miles east of Anchorage hosted nearly 80,000 visitors in 2018.
The best time to visit is summer. Snow often arrives in the park by late September, and the two state roads into the park are not regularly maintained during winter.
2. Smallest national park site
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Hot Springs National Park, Arkansas
Hot Springs is the smallest of the 61 national parks in the country.
The Arkansas park is so small -- just 5,550 acres -- that it could fit into Wrangell-St. Elias National Park nearly 2,400 times.
It would also likely melt its Alaskan cousin: That's due to the park's 47 hot springs coming out of Hot Springs Mountain at 143° Fahrenheit (62° Celsius).
It was first protected as a reservation in 1832 because of the popularity of its geothermal spring water for therapeutic bathing.
Many businesses set up around Hot Springs to provide access to the waters, and the urban park protects the historic bathhouse structures as well as the waters.
Visitors can soak in the traditional Buckstaff Baths (a park concessionaire) and the more modern Quapaw Baths & Spa. Both are on Bathhouse Row, as is the park visitor center in the old Fordyce Bathhouse.
3. Longest cave system in the world
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Mammoth Cave National Park, Kentucky
Called a "grand, gloomy and peculiar place" by early cave guide Stephen Bishop, a slave who eventually gained his freedom, the world's longest known cave system earns its name honestly.
Located in the hill country of south-central Kentucky, Mammoth Cave National Park has more than 400 miles of explored and mapped caves, and more are being documented every year.
Much of the early credit goes to enslaved and eventually free African-Americans, who explored and led tours through the caves throughout the 19th and 20th centuries.
Frozen Niagara is one of a few guided tours to welcome small children, the elderly and people who can only walk short distances, while others are more challenging.
4. Tallest monument in the United States
Gateway Arch in St. Louis
It's known more famously as the St. Louis Arch, the 630-foot monument that was once part of the Jefferson National Expansion Memorial. The memorial was promoted to Gateway Arch National Park in 2018.
And yes, it's taller than the 555-foot-tall Washington Monument in the nation's capital.
Gateway Arch marks the role of St. Louis in the country's westward expansion in the 19th century.
Although formerly named for President Thomas Jefferson and his role in expanding the young country, the park is also a memorial to the enslaved man Dred Scott, who unsuccessfully sued for his freedom in the Old Courthouse.
World renowned architect Eero Saarinen, who had collaborated with his architect father on several projects, entered the 1947 memorial competition independently and won. It was his first major success, but certainly not his last.
A tram ride to the top of the arch's observation deck delivers a spectacular view of the city.
5. Deepest lake in the United States
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Crater Lake National Park, Oregon
Stack up about three Gateway Arches and you've got the depth of the United States' deepest lake.
For hundreds of thousands of years, volcanic eruptions here built up Mount Mazama. Nearly 8,000 years ago, an eruption removed so much material from the mountain's internal chamber that the mountain collapsed.
The remaining caldera, now 1,943 feet deep, is the deepest lake in the United States and the ninth deepest in the world.
The 1.1-mile hike descends 700 feet down to the lakeshore, which is the only spot where visitors can swim. It's chilly, though. The average summer surface temperature is just 55°F to 60°F (13°C to 16°C). If that's not cold enough, the average temperature below 300 feet deep is 38°F (3°C).
6. Tallest peak in North America
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Denali, Denali National Park & Preserve, Alaska
Climbing Denali is not for the faint of heart.
At 20,310 feet high, the highest peak in North America dwarfs Mount Whitney at Sequoia and Kings Canyon National Parks by 5,900 feet.
It's not as strenuous as the hike to the world's highest peak, the 29,029-foot-high Mount Everest in Asia, but climbing Denali is no easy feat.
Hiking for days in arctic conditions, carrying backpacks weighing up to 70 pounds while pulling heavily loaded sleds to summit this Alaskan peak for expeditions lasting up to four weeks are all par for the course.
Once known as Mount McKinley, the official name of the highest peak in North America was restored in 2015 to Denali, the Native Athabascan name it held for thousands of years.
Ohio-born President William McKinley never visited the mountain, which most Alaskans, native and non-native alike, have always called Denali.
The summit often disappears behind clouds but is occasionally visible while driving along the 92-mile Denali Park Road, the only road in the park.
7. The lowest spot in North America
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Death Valley National Park, California
The lowest point in North America -- 282 feet below sea level -- is also the hottest spot in the world.
Death Valley National Park logged a record 134°F (57°C) in 1913, and the park hasn't cooled down much since then. High temperatures are expected to range from 100°F to over 120°F (49°C) in August, which is a normal summer for this long narrow valley walled in by mountain ranges.
And there's no water to spare. The park is also the driest spot in North Ameica, with an average annual rainfall of less than 2 inches That's much less than what other deserts receive.
Sometimes the park warns against summer hiking after 10 a.m. due to the heat.
Even before the cutoff time, "travel prepared to survive," warns the park. Lots of water and sunscreen are in order for visitors heading to Badwater Basin in the Furnace Creek area, where the park drops to 282 feet below sea level.
Too extreme? Spring and winter are supposed to be nice.
8. The world's largest living tree (by volume)
General Sherman, Sequoia & Kings Canyon National Parks, California
Among the renowned groves of massive giant sequoias, one tree stands out.
The largest tree in the world by volume (over 52,500 cubic feet), the General Sherman Tree is the main attraction in Sequoia National Park.
Its circumference at the ground is a whopping 102.6 feet and the largest branch has a diameter of nearly 7 feet.
The General Grant Tree, located about 30 miles away in Kings Canyon National Park, is the world's second largest tree by volume, measuring over 46,600 cubic feet. (The two national parks are managed together.)
They're the largest, but not the tallest. That honor goes to the redwood trees.
9. Highest continuous paved US road
Trail Ridge Road, Rocky Mountain National Park, Colorado
Intrepid motorists are richly rewarded on Rocky Mountain National Park's Trail Ridge Road, the highest continuous paved road in the United States.
Topping out at 12,183 feet, the byway snakes through fragile alpine tundra, giving visitors a chance to witness the unique ecosystem without the huffing and puffing of high-elevation hiking.
Eleven miles of the 48-mile route traverse wide-open expanses above the treeline, where at 11,500 feet evergreen forests give way to 200 species of ground-hugging alpine plants.
Yellow-bellied marmot, bighorn sheep, pika and summering elk go about their business as breathless tourists open their car doors at the Alpine Visitor Center, the highest visitor center in the park system, to blasts of cool air.
Temperatures at the road's blustery summit are usually 20 to 30 degrees lower than they are at the road's bookends in Grand Lake and Estes Park.
10. Busiest national park
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Great Smoky Mountains National Park, Tennessee and North Carolina
The half-million acre park, split fairly evenly between the states of North Carolina and Tennessee, is home to flora and fauna found in both the northern and southern states.
Northern animals and vegetation can be found at the park's higher elevations, while their Southern brethren are represented at the lower elevations.
Many hikers on the Appalachian Trail walk the border between the two states on the trail through the park. Some prefer to catch the view from Clingmans Dome at 6,643 feet or hike up one of the 16 mountains with peaks taller than 6,000 feet.
At more than half a million acres, there's plenty of room to spread out. And if you're looking for something a little less discovered, there are still 419 other National Park Service sites to explore.