(CNN) — A volcanic island in the middle of South Korea's East Sea, remote Ulleungdo island has long been a popular destination among nature-loving South Koreans. But foreigners are just now catching on.

To travel there, you'll first have to navigate a 2.5-hour train ride to Pohang or Gangneung port, followed by a 3.5-hour, stomach-churning ferry ride. At the end of the arduous journey? One of the most beautiful islands on Earth.

Ulleungdo is peaceful and pristine -- a natural refuge that's home to towering volcanic peaks, fascinating rock formations, cedar wood forests, juniper trees, a few tiny fishing villages and a reputation as South Korea's most spiritual destination.

For first-time visitors, here's how to make the most of it:

South Korea's 'Mystery' island

Ulleungdo is nicknamed "Mystery Island" and is known to be a sacred island for the South Koreans. courtesy Kate Springer

Nicknamed Mystery Island for its mystical energy, Ulleungdo is believed to have been formed following volcanic eruptions over 2.5 million years ago.

"Ulleungdo is known to be a sacred island where rich energy of the land and clear energy of the sky meet, and where yin and yang marry," explains Jang Yunhee, a local guide from Toursungingbong.

"For most of its history, the island has been difficult to access and uninhabited by people, so primitive nature and ecology are well preserved. This has added to the island's spiritual reputation."

Between 1400 and 1882, Korea's Chosun Dynasty adopted an "empty-island policy" and ordered islanders to evacuate Ulleungdo for fear of Japanese invasion.

It wasn't until the 1880s, when the Japanese claimed Ulleungdo as its own, that the Korean government set in motion a resettlement plan to repopulate the island.

Arriving in 1883, the first wave of settlers included roughly 54 people. Today, there's just over 10,000 inhabitants.

Throughout the spring and summer, fishing and tourism trades thrive. But come winter, the island more or less grinds to a stop.

Ulleungdo is the snowiest place in South Korea -- on this volcanic island, foot-high snow falls are totally normal.

Even though it's difficult to make the ferry journey, due to rough seas, some travelers prefer to visit the island to ski or simply admire the dramatic, snowy mountain scenery.

Explore by land

A pedestrian suspension bridge leads to the outlying island of Gwaneumdo. courtesy Kate Springer

Famed for its diverse ecology, Ulleungdo surrounds visitors with natural beauty.

One of the best ways to get your bearings is with an easy coastal walk, such as the Gwaneum Island hiking trail.

The one-hour trek takes travelers over a bright blue pedestrian suspension bridge to an outlying island called Gwaneumdo.

The short yet steep hike takes you through ancient forests and silvery grasslands, as you make your way toward viewing platforms framing the sea.

"Gwaneumdo offers one of most beautiful walks in Ulleungdo. It is covered with reed forest," says Jang. "There are three popular observatories around the hike, including views of Bamboo Island and Three Fairy Rocks."

For more experienced hikers, a trek up to Seonginbong -- the island's highest peak at 3,228 feet -- promises a huge payoff on a clear day.

Of the many ways to reach Seonginbong, Jang recommends a walk along the Nari Basin Forest Trail, part of the Nari Basin Geopark.

Located in the center of the island, the basin was created after a volcano eruption millions of years ago. Today, it's best known for its extensive collection of indigenous flora, Mountain Spirit Mineral Spring, and rare mountain vegetables.

"Surrounded by layers of mountains, the Nari Basin is the only flatland in Ulleungdo where many wild mountain vegetables grow," says Jang.

"Within the geopark, you can also admire the cloud fall, layers of clouds which look like waterfalls, and fantastic views in the autumn as the leaves change color."

Then there's Bongnaepokpo Falls, where three tiers of water tumble from a height of 25 meters. The vast majority of hotels and restaurants around the area source their drinking water from this pristine waterfall.

In the surrounding redwood forest, hikers can cool off in front of a "natural air conditioner" formed by holes in the boulders.

Stand in front of the cave-like crevice and you'll feel a steady blast of cool subterranean air, which maintains a consistent temperature of 4 degrees Celsius all year.

For the best views on Ulleungdo, Jang suggests a trip to the Seokpo Observatory -- the only spot on the island where you can enjoy both sunset and sunrise.

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On the water

Ulleungdo is a popular destination for scuba diving, kayaking, fishing and swimming. courtesy Kate Springer

The island is home to clear water that's teeming with marine life, so it's no surprise that Ulleungdo has become a hot spot for scuba diving, kayaking, fishing, and swimming.

Before diving in, we'd recommend taking a scenic boat or fishing tour around the island. From May till November, there are several three-hour tours that depart from Dodong, the main ferry port.

The itineraries typically zig through dramatic rock formations, stop by an old pirate's cave, and afford excellent views of the landscape along the way.

A few tours also provide opportunities to catch fresh red sea bream, butter fish, mackerel and rockfish with experienced local fishermen.

With its clear waters and abundant marine life, the island has become the go-to destination in South Korea for serious divers.

"Ulleungdo attracts divers because of far visibility, large fish and dynamic topography," says Jang. "Throughout the year, a 20- to 30-meter range of visibility is guaranteed, and you can often see as far as 50 meters."

Jang suggests visiting between August and October to experience the best of underwater scenery. "Thanks to the Kuroshio current, you can see tropical fish swimming north with the current."

Kayaking is another way for adventurous travelers to freely explore the waters of Ulleungdo.

Particularly in the waters around Gwaneumdo, on the northeastern coast, kayakers will be surrounded by dramatic cliffs, stoney beaches, and fascinating rock formations such as Elephant Rock.

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What to eat

If budget is no obstacle, we'd recommend eating as much seafood -- especially shrimps -- as possible. courtesy Kate Springer

As you wander through the tiny fishing villages on the southeast coast, you'll likely notice squid drying in the sun and tanks full of squirming shrimp in the shade.

This is a land of superlative seafood, so we'd recommend eating as much as possible during your visit.

Start your culinary journey on a high note with a meal at Chungeumho, in the tiny fishing town of Jeodong. At this mom 'n' pop restaurant, you'll find wooden sharing tables wrapped in plastic and cushioned seats pad the floor.

"The restaurant is run by a fishing company with professional equipment that enables them to bring fresh shrimp from the deep sea [about 50 to 300 meters deep] to the restaurant," says Jang.

"Called Dokdo shrimp, these famous shrimp taste sweeter and have great, silky texture."

They're so fresh, in fact, that these pretty pink crustaceans are presented live tableside before a quick bath in the steamer or fryer.

If budget is no obstacle, visitors can try all three kinds of Dokdo shrimp: Chicken Shrimp, Flower Shrimp and Peach Flower shrimp, which is the rarest.

Named after an island that's part of a territorial dispute between South Korea and Japan, Dokdo shrimp recently shot into the spotlight when they were served for President Trump at South Korea's state banquet in November 2017.

The island is also famed for its wild mountain vegetables. The selection of more 700 varieties is known to lure chefs from all over South Korea.

"Ulleungdo gets more snow than any other part of Korea, but these mountain vegetables still thrive here," says Jang. "As a result, they absorb rich minerals from the wind, sea, and volcanic soil."

"Our wild vegetables have a rich flavor and they're abundantly nutritious."

For those curious about these fibrous herbs and vegetables, Jang suggests lunch at Yayeongjang Sikdang. The open-air cafe sits at the entrance of the Nari Basin Forest Trail, so visitors can sit down for a leisurely san-namul (mountain herb) lunch after a hike.

There's no menu. Instead, simply choose how many vegetable banchan (side dishes) you'd like to try -- some have been dried, fermented, others marinated in chili sauce or vinegar.

There's a set menu that includes namul (mountain vegetables), bibimbap, potato pancakes. The vegetables are typically served in tiny white bowls, alongside warm rice, deodeok-root pancakes, seaweed soup and pumpkin rice wine.

"The most popular is allium microdictyon (myungee na-mul in Korean), which is also called Siberian onion," says Jang. "But it's difficult to get, because it is rare and very expensive. You normally pickle it, then serve it with grilled beef or raw fish."

Another must-try food on the island is local "tiger beef". Sporting a distinct black and orange hide, these rare 'medicine cows' spend their lives grazing on mountain herbs.

"Since the cows grow up eating wild vegetables, the beef has unique flavor," says Jang.

Try it at Ulleung Yakso Sutbul Garden, where an on-site restaurant serves up sirloin and bulgogi, as well as a few other local specialties.

Where to Stay

The newly opened KOSMOS Healing Stay is designed to mimic the Yin Yang sign. courtesy Kate Springer

The island is full of tiny guest houses and a few resorts, but recently opened KOSMOS Healing Stay is by far the most visually striking.

Opened in 2018, the hotel sits on a sheer cliff in the shadow of Songgot-bong mountain (dubbed "ice pick peak" in Korean).

Designed by Chanjoong Kim of The System Lab, a Korean architectural firm, the hotel is shaped like a spiral to mimic the Yin Yang sign. It's also the first building in the world to have been constructed by pouring ultra high-performance concrete (UHPC) into a mold on site.

With this innovative material, the stark white walls are just 12 centimeters thick and have a light, airy feel thanks to high vaulted ceilings. From there, the interiors feature natural volcanic stones, terracotta, and bespoke wooden furniture.

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Each room at the villa is dedicated to one of the five elements, and guests are assigned a room based on their personal astrology chart in order to enhance their 'chi', or energy flow.

Jang says the hotel has excellent feng shui, thanks to its position between the mountains and sea.

"It is abundantly clear that this mountain holds a strong energy," says Jang.

"Koreans believe that a location like this, with a strong chi (energy), can rejuvenate people and help their wishes come true."