Liège-Bastogne-Liège, or La Doyenne, which is held this Sunday, is the oldest and, many would say, the toughest of the spring Classics.
It is also the one in which the Grand Tour contenders tend to show their mettle. It is almost as though, after the phoney wars of San Remo, Flanders and Roubaix, the climbs of the Ardennes provide the setting for a full dress rehearsal ahead of the Giro and Tour.
Timing is a factor, too, of course. Following the other Ardennes Classics - last Sunday's Amstel Gold Race, and Wednesday's Flèche Wallonne - Liège is the final big one-day Classic, and the best chance for stage race specialists to test their legs before the season moves into its next phase: the week-long stage races that act as a prelude to the Grand Tours.
Liège is the final big one-day Classic, and the best chance for stage race specialists to test their legs before the season moves into its next phase.
Quotes of the week
Not that a Grand Tour contender usually wins Liège-Bastogne-Liège and a Grand Tour in the same year. The last to do so was Danilo di Luca, who did the Liège-Giro double in 2007, albeit against a shadow of suspicion (he tested positive in 2009). Before him, Evgeni Berzin did the same double in 1994. Incredibly, the last man to do the Liège-Tour de France double was - who else? - Eddy Merckx in 1972.
But we have become used to seeing Grand Tour contenders stretch their legs, as the Schleck brothers, Andy and Fränk, did last year. Together they escaped with Philippe Gilbert, who, not surprisingly, made mincemeat of them on the uphill finish. The year before that, Cadel Evans was fourth, with Andy Schleck fifth and Fränk eighth.
This year, though, it is more difficult to forecast which of the riders we expect to shine in Italy and France in the summer will also shine in La Doyenne... which raises an important point: that there appears to be a dearth of in-form Grand Tour contenders.
In the absence of the currently suspended Alberto Contador, Andy Schleck should be the rider everyone is talking about. Well, they are, but for the wrong reasons. So far his best placing in 2012 is 22nd in the Circuit de la Sarthe in early April. The Amstel Gold Race often provides an indication of form ahead of Liège: Andy was 91st.
Fränk looks in slightly better shape. He was 12th on Sunday: his best performance of the season.
What of the others? Evans, last year's Tour winner, didn't finish Amstel and has pulled out of Liège with a sinus infection. He won the Critérium International at the end of last month but otherwise has not seemed the force he was in the early part of the last two seasons.
Ivan Basso, whose big goal this year is supposed to be the Tour, has had a miserable start. His highest placing? 90th in the opening time trial at Paris-Nice. Then he pulled out on stage six, and also failed to finish the only other race he has started, the Tour of Catalonia.
Four riders stand out: Bradley Wiggins, who will miss Liège but will ride next week's Tour of Romandie (his first race with Mark Cavendish in Team Sky colours), Vicenzo Nibali, who may ride the Tour (much will depend on the form of his teammate Basso), Tommy Voeckler and Sammy Sanchez. Sanchez, fifth in last year's Tour, is having a barnstorming year, and so is Voeckler, who was fourth.
Voeckler's performance to attack solo and win last week's Brabantse Pijl was extraordinary, and he followed it with fifth at the Amstel (Sanchez was seventh after a broken chain, a bike swap, and a late chase).
The most fancied riders for Liège seem to be Joaquin Rodriguez, Philippe Gilbert, whose form is returning, and Alejandro Valverde.
I can't find much mention of Voeckler, but I think he is a rider who is not only in great form, but who has also learned an important lesson from last year's Tour de France, where he lost his chance of finishing on the podium by riding (characteristically) recklessly in pursuit of Contador and Schleck on the stage to Alpe d'Huez.
It was interesting that he said, after Amstel, that, "I held myself back; I raced a little against my nature." He still needs to attack to win, of course. But what matters is knowing when to attack. If he gets that right on Sunday then perhaps he can land the biggest victory of his career.