(CNN) — Forget the ocean. In Ibusuki, a beachside city on Kyushu Island in Japan's subtropical south, it's all about the sand.
Not the dark color of the sandy granules or even the length or width of the beaches, but rather the intense infusion of minerals from volcanic hot springs along the coast.
The black sand is actually warm to the touch and soothing to the skin of anyone who travels here to engage in a ritual the Japanese call suna-mushi (sand bathing).
Clad only in a light yukata kimono, beachgoers -- with assistance from attendants at spas and resorts along the shore -- cover their bodies with the healing sands.
Kaimondake: Mt. Fuji of Satsuma
Perched on Kagoshima Bay, Ibusuki Beach sprawls across the southern end of the Satsuma Peninsula, an area renowned for its volcanic activity.
Looming in the distance is Kaimondake -- dubbed the "Mt Fuji of Satsuma" because of its almost perfect conical shape. Although it last erupted in the 9th century, it's still considered an active volcano.
Nearby Lake Ikeda is also volcanic in origin, a large caldera that flooded thousands of years ago. Ikeda is the legendary home of the Japanese version of the Loch Ness Monster, a myth no doubt inspired by the fact that one of the lake's bona-fide inhabitants is a species of freshwater eel that grows to two meters (six feet).
So it comes as no surprise that Ibusuki is literally a hot spot for geothermal activity.
Strewn along the beach are people half buried in simmering sand, uniformed sentinels standing over them with shovels. Far from being macabre, Ibusuki beach is a rare natural spa with warm sands heated by the nearby volcano.
Proved by science
For more than 300 years, Japanese have traveled to Ibusuki's shoreline in search of a sandy cure for rheumatism, back pain, post-stroke paralysis, hemorrhoids, asthma, diabetes, menstrual disorder, infertility, anemia, constipation, obesity and all sorts of other things the warm sand (50-55 degrees Celsius) is said to cure.
This healing power lured both ordinary Japanese and historical figures like Shimazu Nariakira, a powerful daimyo (feudal lord) who built a manor house on the edge of one of the hot springs near Ibusuki City.
Nearly two centuries later, the main pool at Nigatsuden Onsen hot springs bears the Shimazu family emblem.
In modern times, suna-mushi has also evolved into a beauty treatment, a means to moisturize the skin via metasilicic acid and calcium ions in the sand.
Bent on proving the veracity of these health and beauty claims, Japanese researchers have put the black sands through a battery of scientific tests in recent years.
For instance, a study by the medical department at Kagoshima University determined that inhaling the steam that filters through the sand increased cardiac output and improved blood circulation by a factor three to four times greater than the steam generated by average hot springs.
Japanese have been traveling to Ibusuki to sand bathe for more than 300 years.
Kagoshima Prefectural Visitors Bureau
How to enjoy sand bathing
Many of the spa hotels offer a choice of shaded suna-mushi pavilions or sand bathing in the open air with an umbrella or towel to protect your face from the sun. Both hotel guests and day visitors are welcome at the sand baths.
Changing rooms are provided for you to slip out of your street clothes into a yukata, which is made with material thin enough to expedite transfer of the volcanic steam from the sand into your body.
Wearing your bathing suit or other garments beneath the kimono, while not forbidden, is discouraged because they may inhibit that transfer.
Making your way down to the beach, pick a spot (either in the sun or shade) and simply lie down. Shovel in hand, a resort or spa attendant will quickly arrive. They'll make sure a towel is fixed around your neck to prevent the gritty stuff from getting into your face, and then literally bury you up to your chin in warm, dark beach sand.
Ten to 20 minutes beneath the sand is recommended -- enough time to inhale a fair amount of geothermal steam and get the sweat glands flowing to expunge toxins from your body.
Freshwater showers await to wash the sand from your body, after which you're free to sink into the relaxing hot spring pools -- the final part of the Ibusuki beach experience.
Kaimondake, the Mt. Fuji of Satsuma.
Kyushu Tourism Promotion Organization
Where to stay
The Satsuma Denshokan on the grounds of the upscale Hakusuikan hotel (and just steps away from the beach) is a museum of local art, culture and history housed inside a traditional Japanese structure that could easily double as a medieval temple or palace.
At the north end of Ibusuki Beach, a sandbar connects the mainland with Chiringashima. Extreme low tides between March and October expose the sandbar to sunlight. Visitors can hike the 800 meters over to the wooded island. Another remnant of the region's volcanic past, Chiringashima offers tide pools, short hiking trails and rugged sea cliffs.
Other spas are located along the waterfront in the middle of Ibusuki City, including a popular public spa called the Saraku Sand Bath Hall. Charging just 1,080 yen ($10) for a sand bath, the hall includes indoor hot springs and steam rooms, and its own black-sand beach area. Away from the hustle and bustle of the main strand, Healthy Land Tamatebako hot springs and spa is located on Yamagawa Beach on the city's south side. What sets this place apart from the other black-sand spas is a secluded coastal location with awesome views of Kaimondake volcano and the fact they offer ice cream as a cool complement to the searing sands. A black-sand bath is especially soothing after climbing 924-meter (3000-foot) Kaimondake or playing around of 18 at Ibusuki Golf Club's Kaimon Course, which sprawls along the bottom of the volcano.