One word that cannot be used to describe to the Giro d'Italia is predictable - and this year's event, the 91st edition in the race's history, should push the boundaries of uncertainty even further.

Sweeping from Sicily in the south to the Alpine summits and lakes of the north, the three-week 3,424-km slog passes through almost every region of Italy, getting more demanding as the race progresses, and culminating in a last-gasp time-trial into Milan following a week of mountainous terrain and three summit-top finishes.

The deciding 23.5-km ITT - for the event organisers are expecting the Giro to come right down to the wire - will be the fourth race-against-the-clock of an itinerary which is in distinct contrast with that of the more celebrated Tour de France.

Where this year's Tour route has notably less time-trial kilometres than in recent years, the Giro's 73.3kms should ensure that the winner on 1st June of what many say is the most demanding of the Grand Tours will have to be a brilliant individual capable of excelling across all terrains both in and, more importantly, out the peloton - rather than simply a specialist climber.

With a 28-km team time-trial (ideal for the specialists at Slipstream) getting proceedings underway in Palermo, a second, more routine, 36-km ITT in Stage 10 will be followed by the daunting 13.8-km timed ascent of the Kronplatz before the final denouement in Milan.

The Kronplatz, with its 5-km gravel ramp at a hellish gradient of 24%, is as much a part of Giro folklore as Alpe d'Huez is for the Tour - and yet thanks to the hefty schedule after Stage 16, it should not prove as decisive in the overall classification as the last time the Tour took on Alpe d'Huez in an ITT, when Lance Armstrong blew away Ivan Basso and Jan Ullrich on his way to victory in 2004.

Many of the Giro's staunchest supporters claim the magic of the race lies in its unpredictable nature, which sets it aside from a race like the Tour where a rider like Armstrong can dominate over a seven-year reign.

Indeed, the Giro has only been bossed by a single rider on three occasions - with Eddy Merckx, Alfredo Binda and Fausto Coppi all winning the race on five occasions.

Such is the traditional desire of the race organisers to keep the event fresh and exciting, Binda was even paid to forego the 1930 race amid fears that his four consecutive wins had waned the interest of the Tifosi, or fans.

The Tifosi play an extraordinary role in the Giro, and one which differs from the hoards that line the French roads in July. While no bicycle race can beat the Tour for sheer spectator numbers, the type of supporter the Giro entices is not wholly similar.

Often dubbed 'the people's race', the Giro is celebrated for being ostensibly more interesting, more competitive, open and exciting that its Gallic cousin. It is also a race which attracts grassroots cycling aficionados (pictured).

One ex pro, Davide Cassani, once noted that the main difference between the two races was in the type of spectator. Where the Tour attracted all and sundry (and the picnic table), the Giro attracted cyclists - a fact borne out by the amount of bikes strewing the verges of the route.

If the Tifosi can fully appreciate the effort of each rider in the bunch, Cassani said it is because many of them have themselves already ridden up the very same climb to reach their vantage point.

Another factor which considerably differentiates the Giro from both the Tour and the Vuelta A Espana is the weather.

While the Vuelta habitually crosses parched desert-like plains at temperatures as high as 40 degrees, and the Tour weaves its way through the French countryside under a frequently warm July sun, the Giro takes place in the meteorologically fickle month of May, when rain, wind and even snow can be a major factor. And that is not to mention the poorer quality of roads.

One thing, however, that is easy to predict about the Giro in recent years is the nationality of the rider crossing the finishing line in the Maglia Rosa, or pink jersey.

Since the Russian Pavel Tonkov won the race in 1996, the winner has been an Italian. But while the likes of Paolo Savoldelli, Gilberto Simoni and Ivan Gotti have two victories to their names, no one has recorded back-to-back triumphs since the Spaniard Miguel Indurain in the early 90s.

For that trend to be reversed, reigning champion Danilo Di Luca will have to produce the race of his life over the next three weeks.

The former Liquigas rider will have his work cut out if he wants to make an impression following a recent ban while he was under investigation for his alleged involvement in the Blood for Oil doping scandal.

Although beefed up by Savoldelli, Di Luca's new team - the virtually all-Italian Irish outfit LPR Brakes - lacks experience on the main stage, while Di Luca, for all his bullish pre-race confidence, is short of practice.

The same could be said for Tour champion Alberto Contador, who will now race his debut Giro following Astana's 11th Hour invitation to the race, but who had not been looking to hit peak form until July.

Following their dramatic exclusion from the Tour, the Luxembourg-based, Kazakh team will certainly have a point to prove - and with the likes of experienced veterans Levi Leipheimer and Andreas Kloden alongside the young Spaniard, the men in turquoise and yellow will surely be the team to watch.

Unless, that is, the race experiences the kind of debacle that the team brought to the Tour last year, when its leader - and race favourite - Alexandre Vinokourov was dismissed for doping offences alongside two other team-mates, and Astana were swiftly dumped out of the race accordingly.

Race organisers RCS Sports, however, are confident that this year's Giro will be a clean event. Their insistence on each of the 198 riders carrying a biological passport is admirable and everyone involved will hope that the headlines are made on the roads - and not in the testing laboratories.

Other contenders will include Russians Vladimir Karpets and Denis Menchov, and Italians Franco Pellizotti, Vincenzo Nibali, Riccardo Ricco and the evergreen Simoni.

In the battle for the green mountains jersey it will be interesting to monitor the performance of Mauricio Soler following the Argentine's storming Tour debut last year, whilst on the flat, in the absence of sprint king Alessandro Petacchi, the likes of Daniele Bennati, Erik Zabel, Mark Cavendish and, of course, Robbie McEwen, will battle it out for the cyclamen points jersey.

Felix Lowe / Eurosport