The cobbled Classics have their secteurs pavé and their bergs. Paris-Roubaix has its gruelling cobbles and combative racing. However, the oldest Classic of them all is set apart by the amount of climbing the riders must conquer if they are to have any hope of victory when they finally return to Liège.
Three-time Vuelta a España winner and former Hour Record holder Tony Rominger once added up all the changes in altitude in Liège and reckoned the total came to something like a solid Alpine stage of the Tour de France.
So, here are the climbs counting down to the finish at Liège, a climb-by-climb guide to the hills of the last Spring Classic, 258km long and barely a metre of flat on it.
10. Côte de La Roche-en Ardenne
Average gradient: 6.2 per cent
The first of the major tests on the route, it'll be the only classified climb en route to Bastogne. Far from the toughest in the race, it remains a fairly steady gradient between 5.5 and 7 per cent throughout.
Winding up through the woods outside of La Roche-en Ardenne, the major challenge for the peloton will be navigating it's narrow road. At only 78.5km gone when they hit the climb, the emphasis will be placed on staying out of trouble and near the front for the contenders and their teams.
9. Côte de St Roch
Average gradient: 11.2 per cent
The first hill on the way back to Liège from Bastogne, the second on the day's menu - and where the racing starts to get really serious. At the foot of a long sweeping descent into the town of Houffalize, a sharp righthander from a central roundabout leads up a short, well-surfaced and largely straight climb.
The catch is the gradient - viciously steep throughout and after such a fast previous descent, sure to split the bunch.
8. Côte de Pont
Average: 10.5 per cent
A relative unknown on the Liège course and the first of three chucked in because there's maintenance work on the traditional route over the Wanne, Stockeu and Haute-Levée climbs. This won't have any significant effect on the outcome the race but with 168km in the legs, it could see the first big wave of riders shed out the back on its steep slopes if they made it over the climb 20km earlier.
7. Côte de Bellevaux
Average: 6.8 per cent
A winding, fairly well surfaced road up through the Luik region, the average gradient is a bit misleading. The climb gets up to 11.5 per cent maximum, but you can still expect the pros to ascend this rural climb at around 21kph. Again, this here due to road works on the normal part of the course.
Your essential guide to the Ardennes Classics
Côte de la Ferme Libert
Average: 12.1 per cent
The last of the filler climbs for 2017 comes at 180km covered and it looks a bit brutal. Riders will climb up through the tree lined climb that just seems to get steeper over the first half, reaching 17 per cent slopes in the middle section. It eases off again before kicking up once more towards the end. While this won't be somewhere for attacking, it'll be another crucial moment for those who want to be in contention to make sure they're staying safe towards the front as riders begin drifting backwards.
6. Col du Rosier
Average: 5.9 per cent
This climb should be more famous than it is. Just like almost every hill in Liège-Bastogne-Liège, it starts with a right-hander, then winds its way upwards with almost no breaks. Reasonable road surface, but lots of sharp bends, mud and sudden sharp kicks upwards. A really tough climb.
5. Col du Maquisard
Average gradient: 5 per cent
With a fairly decent road surface and some width to play with, this'll be one of the less stressful climbs for the bunch, but could still see some attacks coming around 50km from the finish.
Winding out of the village of La Reid in the Wallonia countryside, this is more likely to just be another addition to the attrition rate of the pack rather than a deciding moment in the race.
4. Côte de La Redoute
Average: 8.9 per cent
The most emblematic climb of the whole of Liège-Bastogne-Liège, and when it finished in the city centre, the one which almost always decided the race.
Traditionally it's where the big favourites know they have to be at the front and getting in the moves - and we're not surprised. Starts off gently enough in the middle of a small town, underneath a motorway bridge then a right-hander is where it really begins to steepen.
Narrow and twisting, there are sudden major changes of gradient which make it really strength-sapping. The fans will be three or four deep on either side of the road here and there really is nowhere to hide. Lose the wheel of the guy in front on this climb and you're gone. Probably forever.
3. Côte de la Roche-aux-Faucons
Average: 11 per cent
Only added to Liège-Bastogne-Liège in 2008, replacing the Côte de Sart Tilmont and is another pivotal moment for splits in the bunch.
This one is a monster. It starts by going over a level crossing and then kicks upwards with constant changes of gradient and corners galore. Narrow, twisting, there's even a huge road drain running right across the middle (yes, the middle) of the road at one point. The surface isn't as bad as La Redoute, but it's getting there.
As if that weren't enough, after the official summit, there's another kilometre of a winding unclassified climb, not as difficult, following straight after a kilometre of fast descending and a short flat section. Then it's onto a long, long descent into one of the grimiest suburbs of grimy Liège.
2. Côte de Saint-Nicolas
Average: 8.6 per cent
Where the race always - but always - splits apart and the final attacks come thick and fast. This time, it's back to being the final climb, which will mean it'll be the bit you don't want to miss.
Running through a grimy suburb of Liège, this is basically a succession of steep corners with nothing between. Known as little Italy because of the number of immigrants from that country who live on the street, it's not the toughest of the Liège climbs in itself, but so steep it can leave you winded.
After almost 250km of racing, very hard to handle - except for a very few top names.
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