The 2016 Tour de France features an impressive 28 mountain passes, which will test the legs of even the best climbers in the peloton.
With mountains coming as early as stage five, there is little respite from the hills in next year's route, with it even featuring an uphill time trial to further add to the pain.
Not all of the mountains will be decisive in deciding the winner of the Tour de France, but there are a handful that could see a rider's hope of winning come crashing down.
Here we take a look at seven of the most important ascents of next year's Tour.
Pas de Peyrol (stage five)
A throwback to Tours of years gone by, the first mountains of the 2016 route come as early as stage five, and there are some pretty serious climbs on the roads to Le Lioran.
The Pas de Peyrol is the first real climb of the Tour, but unlike in 2015, where Chris Froome burst away on the first climb to extend his lead, it's unlikely that a major move will be made here.
Coming 180km into the 216km stage, the Puy Mary climb has a brutal sting in its tail, with the final three kilometres of the ascent averaging over 11.5 per cent in gradient - a good way to get your legs warmed up.
It is followed by the shorter, but no less steep Col de Perthus and then the relatively sedate Col de Font de Cère to finish off.
Here will be where the GC favourites will start their battle.
Col de Peyresourde (stage eight)
The mountains come thick and fast on stage eight, with another visit to the infamous Col du Tourmalet, although coming at 86km into the 183km stage it's unlikely that the mountain will have much impact on the race.
The last of four climbs on stage eight will likely be where any attacks are made. The 7.1km ascent features pretty steady gradients of seven and eight per cent, but the descent off the other side might be where the stage is won.
This could be a stage that the breakaway stays away, like they did on the Tourmalet stage in 2015, but there are still time gaps to be had among the favourites.
Andorre Arcalis (stage nine)
After the mountainous stage eight comes the incredibly mountainous stage nine - the last before a well earned rest day. A jaunt into Andorra means very high mountains and some serious ascents, with five categorised climbs on the route.
The stage starts with a massive ascent of Port de la Bonaigua, but the final climb up to Arcalis is a bit of a beast.
While only officially 10.1km, the roads are pretty much uphill for the last 20km of the route, with the last 10km averaging 7.2 per cent. The gradient will be one challenge, but so will the altitude - Arcalis sits 2,240m above sea level.
Mont Ventoux (stage 12)
Mont Ventoux doesn't really need much of an introduction, but the famous climb from Bedoin is back again for the 2016 Tour after a three-year absence.
Froome won up the ascent of the Bald Mountain three years ago and will likely be aiming to do exactly the same again.
What stands between him and the top is a mere 15.7km climb, averaging nearly nine per cent. It starts hard and doesn't get much easier, with the final two kilometres an 9.5 per cent.
Not for the faint of heart.
Finhaut Emosson (stage 17)
While in Switzerland the peloton will climb some pretty decent mountains, including the one up to the Lac d'Emosson.
Like many of the mountains in next year's Tour route, the Finhaut-Emosson climb has a sting in its tail, with the last two kilometres over 10 per cent, with a mixture of eights and nines on the rest of the 10km ascent.
If that wasn't hard enough, the riders have to climb the 13km Col de la Forclaz to even get to the base of the Emosson climb. A seven kilometre descent from the Forclaz will help them get some energy back in their legs, but we're at the business end of the Tour now, so everyone will be going flat out.
St Gervais-Mont Blanc (stage 19)
Sitting in the foothills of Mont-Blanc, the Saint Gervais climb could be one of the prettiest on this year's route, but the riders won't have much time to take in the scenery.
At 9.8km, the Bettex climb starts with a kilometre of just under 13 per cent, followed by a kilometre of just under 11 per cent.
There's about 250m of respite at the end of the third kilometre before the road ramps up again. This climb is definitely one where we'll see attacks on the leader, with the sheer relentlessness likely to cause time gaps.
Col de Joux Plane (stage 20)
When it comes to relentless climbs, there are few tougher than the Col de Joux Plane - one of the hardest climbs to ever appear in the Tour de France, according to Daniel Friebe in his Mountain High book.
A regular feature in the Tour in the 80s, Joux Plane has only appeared twice since 2000, and it is where Lance Armstrong famously bonked in his second Tour 'win' at the turn of the Millennium.
Starting in the forest on the way out of Samoens, the roads rise up to nearly 10 per cent and don't get much shallower for the next 11.6km.
An intimidating five kilometre stretch close to the summit rarely goes below nine per cent. Once the riders have reached the summit (where there's a lovely lake and cafe for the spectators) it's the twisting and turning descent down into Morzine, where the winner of the Tour de France will be decided.
Ben Swift successfully defends British National Road Race title
The Ineos rider outlasted Fred Wright on the Michaelgate climb to the finish line
By Jonny Long •
Pfeiffer Georgi wins British National Road Championships
The DSM rider attacked up the Michaelgate climb to seal the victory
By Jonny Long •
Extra security meant Bern's hosting of Tour de France cost £500,000 more than expected
Tour de France cost Swiss capital of Bern more that it thought it would
By Jack Elton-Walters •
Vincenzo Nibali slams critics of his Tour de France performance
Vincenzo Nibali says he's 'not a robot' and can't be expected to compete with those specifically targeting the Tour overall
By Gregor Brown •
Tony Martin reveals why he had to abandon Tour de France on Champs Élysées
Tony Martin made it all the way to final circuits in Paris on stage 21 before being forced to pull out of Tour de France
By Richard Windsor •
This is what it took to fuel Chris Froome and Team Sky through the Tour de France
Team Sky and Chris Froome ate a combined total of 1,000 energy gels and more than 500 bars during their 2016 Tour de France success.
By Richard Windsor •
Chris Froome wins 2016 Tour de France as André Greipel takes final stage
Chris Froome takes his third Tour de France victory in Paris on Sunday as André Greipel takes the final sprint showdown on the Champs Élysées
By Nigel Wynn •
The moments that won Chris Froome the 2016 Tour de France
We look back at the key points from the 2016 Tour de France that won it for Chris Froome
By Stephen Puddicombe •
Rival teams praise 'super' Sky at the Tour de France
Chris Froome did not win the Tour de France on his own, but was backed by eight Sky team-mates to make an unbeatable combination that is the envy of rivals
By Gregor Brown •
Chris Froome and Peter Sagan's special bikes for Tour de France final stage
A yellow Pinarello and a green Specialized for Chris Froome and Peter Sagan to mark their classification wins in the 2016 Tour de France
By Nigel Wynn •