'Only a fool climbs Mount Fuji twice,' an old Japanese saying goes. High on its slopes, beneath swirling evening mists and the occasional rain shower, stands a small hut with a sign outside that reads 'Ikeda'. It is warm inside, and under the glow of a gas lamp a kettle boils over a kerosene heater. In a hushed voice, Ikeda-san, its elderly caretaker, stands at the door in a brown hapi, or traditional Japanese cotton jacket, ushering climbers inside. For two months of the year, during the official climbing season, which lasts until the end of this month, he and his wife run a modest shelter, charging climbers 5,000 yen (HK$333) for a bunk bed to rest in before they make their final assault on the summit in time for sunrise. Chatting amiably over a cup of green tea and with a background chorus of contented snores coming from the bunk room, all seems calm on Japan's most sacred mountain, which is known simply to its citizens as Fuji-san. Yet, when I mention the word funka, which means 'eruption', and the possibility of one altering Mount Fuji's exquisitely shaped cone forever, Ikeda-san's expression turns pensive. 'Nothing in this world remains the same forever - not even a 100,000-year-old mountain,' he says. Speculation that the largest of Japan's 86 active volcanoes, which lies at the junction of three tectonic plates, is about to blow its top is rife as it reaches the completion of what scientists are calling a 300-year volcanic cycle. The last time Mount Fuji erupted was in 1707, during the Edo Period: 300 years ago. Those who monitor the mountain's moods have been encountering increasing amounts of activity, namely in the frequency and intensity of tremors beneath its peak. In 2000, seismologists received a jolt when the monthly average of about 20 tremors leapt to 200. Earthquakes are a prelude to magmatic pressure being released. Mount Fuji is classified as an active volcano but the official government line is that any risk of eruption remains low. Yet comments by Masaaki Kimura of the seismology department at Ryukyu University, in Okinawa, about the recent build-up of magma inside Mount Fuji having already reached critical levels have provided those living in Tokyo, 100km away, with food for thought. So if you want to climb Fuji, now could be the time. Approximately 200,000 people from around the world make the ascent every year. Thousands of Japanese attempt to reach the summit of their most revered mountain every day during the climbing season. Most climb to witness the rising sun, others just to be able to say they did it, some to contemplate their existence. Depending on weather conditions and fitness levels the climb takes four to eight hours, the descent two to five hours. Four major hiking routes lead to the summit and each has 10 stations. Sealed roads lead to the fifth stations, at 2,300 metres, where buses from Tokyo terminate. The most popular route is the Yoshida-guchi, which can be reached by bus directly from Shinjuku, in downtown Tokyo. The second most popular, thanks to its proximity to the summit, is the Fujinomiya route. Four routes also lead from the base of the mountain: the Murayama route is the oldest and the Yoshida route still features shrines, tea houses and huts. Most ascents begin in the afternoon, which allows climbers to take a bunk bed at a hut near the summit and begin the final leg in time for sunrise. Plenty of food and water are needed for the journey, as well as a torch and a raincoat. Those wearing contact lenses should consider goggles, otherwise the volcanic dust will turn eyeballs into ashtrays. If a major eruption does occur, what will happen? Researchers at the Tokyo Industrial Research Institute's department of geosciences paint a grim picture for densely populated regions such as Tokyo and Yokohama should large amounts of ash billow into the sky and be caught by strong westerly winds - those on the mountain at the time don't even enter the picture. The scientists believe airborne ash would cause severe damage, putting Narita Airport, the Shinkansen train lines and main highways out of commission for days, possibly weeks, owing to the clean-up process. Water and sewerage systems would be affected and power outages would certainly occur. Despite the warnings of doom, Fuji still looms large as a national symbol in the collective psyche of the Japanese. Ask any school pupil its height and '3,776 metres' is the automatic response. Older Japanese relate a superstition that anyone who dreams of an eagle, an eggplant or Mount Fuji on January 1 will have good fortune for the rest of the year. Such superstitions cast little light on oddities such as an unusual lack of snow on the summit last winter or unexplained reports ranging from a mysterious drop in the local frog and sparrow populations to villagers complaining of nausea and dizziness. There is plenty to fuel the fires of speculation about Fuji's future as, for the moment, an incessant tide of tourists, rather than climbers, is delivered by bus halfway up the mountainside. Standing in a vast car park surrounded by revving engines, rabid souvenir shoppers, yapping dogs and blaring mobile phones, one can understand the reason behind the mountain's recent rumblings. The din is loud enough to give the gods a giant headache. Getting there: Dragonair ( www.dragonair.com ) flies from Hong Kong to Tokyo.