Archaic, ritualistic and stereotypically Japanese, Sumo wrestling, could easily leave you cold. But experience the energy of a packed auditorium, witness the spectacle of two huge human masses hurtling headlong into each other and you'll be hooked - transfixed in a mixture of awe and disbelief.

When Japanese friends sat me down in front of the television set to watch a Sumo match I can't say I was much impressed, and quickly tired of what seemed a very brief and futile scrap between two staggeringly fat wrestlers. But given that I was visiting Tokyo during one of only six annual tournaments, I decided that seeing this major cultural event in the flesh - and loads of it - could not be missed. I hoped it might even give me a better understanding of the Japanese psyche.

Tokyo's National Sumo Stadium, in Ryogoku, eastern Tokyo, is a few minutes from the Metro (Ryogoku stop) and towers over an otherwise uniform urban landscape. The build-up to the match begins well before you step inside - walking from the Metro to the stadium, you are more than likely to find yourself accompanied by one or two contestants who stroll nonchalantly along with a certain arrogance and presence that only such an unearthly bulk can achieve.

The thought of these men living and training in their Sumo "stables" makes them seem in even more of another world than they already appear as they thunder down the street.

Sumo giants, who weigh an average of 300lb (21 stone), are considered national heroes and sex symbols. They earn big money, command respect and, being such a prestigious and wealthy catch, tend to marry the most petite and stunning of Japanese women.

Having said that, their image took a serious pummelling this year, with allegations of corruption, tax evasion, yakuza (Mafia) connections and fight-rigging. Fans were devastated, particularly as the claims came from an ex-champ, Onaruto, who mysteriously died shortly before he was due to give a press conference - but not before he wrote his book, Bout-Rigging, which accused the yakuza of buying wrestlers and rigging matches.

Walking into the stadium was like entering a temple. Far-off chanting led me to where the action was taking place: a vast space with seats reaching up to the gods and down to the central ring where two contestants - looking deceptively diminutive in the distance - squared up to each other, ready to charge. The stadium was largely empty. It was midday at the end of only the first week - which meant that, for a couple of hours at least, there was plenty of room in all the choice corporate seats which no amount of money can buy.

Luckily I'd come equipped with a bento box - this is a tasty Japanese lunch box with rice, vegetables and a choice of meat or fish - so settled down on a floor cushion, chopsticks in hand, eyes glued to the stage to see what happens when an irresistable force hits an immoveable object.

The scene was striking. The medieval splendour and ancient rituals were totally at odds with 20th-century Japan - a country where cash machines talk to you and one of the latest female pop stars to be inundated with fan mail is a virtual reality computer creation.

The atmosphere inside the stadium is very relaxed and officials are little in evidence, so if you want a better view, your best bet is to grab your camera and stroll down to the front, where you can stand at a safe distance from tumbling wrestlers and catch all the skill of the fight.

Originally, Sumo was a religious Shinto ceremony carried out for the benefit of the Gods. The ring is made of clay and outlined with a thick, circular rope. The rules are simple: the first to be pushed from the ring or to touch the ground with any part of his body other than the soles of his feet is the loser.

The lead-up to each fight is mesmerising, with lots of salt-throwing to purify the ring and thigh-slapping and foot-stamping to ward off evil spirits, honour the gods and psych out the opposition. The rounds only last a couple of minutes each, but the bursts of energy are fast and furious. Contestants shove, slap, grapple or get a good belt grip to send their opponent flying from the ring.

The battle is fierce, as only those at the top of this profession get any financial rewards and success is far from guaranteed. As the higher- ranking wrestlers take to the ring, the seats fill up, the tension rises and the crowds, stocked up with copious amounts of food and drink, become increasingly rowdy.

I never actually made it to my seat, which I assume was way up in the gods, and, not knowing one wrestler from the next, did not wait to see who were that day's champions. Instead, I left feeling culturally sated, charged up for a Friday night in the bustling all-night bars of Shinjuku, and with a slightly clearer idea of what makes the Japanese tick.

Weighty matters

Getting there: The cheapest way to reach the Japanese capital is on an air ticket to Australia. For example, Flightbookers (0171-757 2468) has a fare to Sydney via Tokyo of pounds 686 on All Nippon Airways for departures today; you save pounds 60 for mid-week travel, but be warned that availability is limited. You are allowed a stopover in Tokyo en route in wither direction. If you cannot travel to Australia, Creative Tours (0171-495 1775) sells a discounted fare of pounds 809 non-stop on Japan Airlines.

Getting Sumo tickets: This month's Sumo tournament in Tokyo starts tomorrow and runs to Sunday 26 January. The National Sumo Stadium is in eastern Tokyo, and is very close to Ryogoku, on the JR Sobu line. If you have any problems, the Japan National Tourist Organisation's tourist information centre has staff who speak English and are very helpful (3502 1461).

The next two tournaments in Tokyo are: 9-23 March and 11-25 May.

It is not necessary to get up at the crack of dawn to queue for tickets, as you will invariably be told by everyone you ask. Not, at least, if you go in the first week, or early in the second, before the big players start coming face-to-face in the build up to the final battle. Tickets can be bought on the day from the box office, at a cost of only 1,500 yen (pounds 8).

Getting information: Japanese National Tourist Organisation: 5th Floor, 20 Savile Row, London W1X 1AE (0171-734 9638).