Chris Froome will embark upon the "toughest challenge" of his career when he begins his quest to win a third Tour de France title on Saturday.
The Team Sky rider, 31, is favourite to become the first man in 20 years to win consecutive Tours.
He faces stiff competition from two-time winner Alberto Contador and two-time runner-up Nairo Quintana.
"I've got more rivals and the level of my rivals is that much stronger," said the 2013 and 2015 champion.
A climber's Tour
The 3,500km route comprises nine flat stages, nine mountain stages - with four summit finishes - one hilly stage and two individual time trials.
A total of 198 riders from 22 teams will start Saturday's stage from Mont Saint-Michel to Utah Beach in Normandy before heading south to the Pyrenees mountains during the opening week.
The route then takes the riders to the Alps, via the legendary ascent of Mont Ventoux and a stage in Switzerland, before heading for the traditional finish on the Champs-Elysees in Paris on Sunday, 24 July.
Froome said: "The route this year is very much climber-based in terms of even the two time trials we have. One is straight uphill and the other one has two long climbs on it.
"Even though we have time trials, they're time trials where a climber will do well.
"I imagine a lot of people will be looking at that last week given it's so heavily loaded with mountains - stage 17, 18, 19 and 20 - anyone trying to make up time, it will be a great opportunity.
"Whoever's defending the yellow jersey, it will be tough, four days back-to-back like that."
Where will the race be won and lost? Read Geraint Thomas' stage-by-stage guide.
Will Froome win it again?
The 31-year-old has based his whole season around the next six weeks, with the Olympic road race and time trial in Rio following the Tour.
He started his winter training later than usual and has not competed in as many stage races, although he did win the Tour warm-up - the Criterium du Dauphine - as he did in 2013 and 2015.
"It's about delaying reaching that peak form," he said. "In previous seasons, in the spring I'd been in that shape and then basically tried to hang on to it whereas now I feel as if I've only just got there.
"Hopefully it means that because we've delayed everything I'll be able to hang on to it a bit longer, and hopefully into Rio too."
Team Sky principal Sir Dave Brailsford says "there's a real excitement and anticipation for the race".
He added: "If you worry about people ganging up on you, you are not able to focus on yourself.
"We'll make the race and choose our tactics accordingly. It's about being proactive and controlling, rather than worrying about other people."
Team Sky have assembled what is generally regarded as the strongest-ever nine-man Tour de France squad to try to help Froome to victory - a fact that has not gone unnoticed by one of his main rivals, Contador.
"It's not just about beating Froome. It's about beating the whole of Team Sky," said the Spaniard.
Racing for yellow
Chris Froome - Team Sky
Tour pedigree: Helped Sir Bradley Wiggins become the first British winner of the race in 2012 before becoming the first two-time winner last year. Looking to join a group of seven riders to have won three or more Tours de France.
Strengths: 'Froomey' can climb and time trial with the best in the race and has one of the strongest teams ever assembled around him. He is also tactically astute and can adjust his strategy when needed. Froome has delayed reaching his peak form in an effort to also go for gold in the road race at the Rio Olympics.
He says: "I've made a personal goal to be stronger in the third week than I had been in the past."
Nairo Quintana - Movistar
Tour pedigree: The 26-year-old Colombian has twice finished second to Froome, winning the young rider classification on both occasions. Quintana attacked on L'Alpe d'Huez last year and almost snatched victory from Froome. He won the Giro d'Italia in 2014.
Strengths: Sensational in the mountains and an excellent time trial rider, this course will suit 'Nairoman' perfectly. He developed his technique while cycling to school in the Colombian town of Combita, which has an altitude of nearly 3,000m. After sharing team leader duties with Alejandro Valverde in 2015, Movistar are putting all their efforts behind him this year.
He says: "I have to win the Tour and this is the right time. I've gained another year of maturity, we're prepared and I'm ready for it."
Alberto Contador - Tinkoff
Tour pedigree: Twice a winner, in 2007 and 2009, the Spaniard had a third victory in 2010 taken away for doping. 'El Pistolero' has also won two Giros d'Italia and three Vueltas a Espana in a glittering career. Aged 33, he had said he was targeting one last yellow jersey and Olympic gold in Rio before retiring but the rumours are that he may continue.
Strengths: An explosive climber always looking to attack in the mountains, the uphill time trial routes are likely to suit him. Illness left Contador below his best in 2013, he broke his leg in 2014 and came into the 2015 race underpowered after winning last year's Giro d'Italia. He has focused his entire season on the next three weeks.
He says: "I've always liked to be competitive and I guarantee I will prepare 100% for the Tour de France."
Fabio Aru - Astana
Tour pedigree: 'The Little Angel' is making his Tour debut and will be 26 on Sunday. However, he is developing into an excellent stage racer, having won last year's Vuelta a Espana and finishing runner-up to Contador in the 2015 Giro d'Italia.
Strengths: A superb climber, so the mountainous route should suit him, as will the hilly time trials. He also has fellow Italian Vincenzo Nibali, the 2014 Tour winner, in his team as an expert guide.
He says: "I'm maturing quickly, both physically and through experience. I won races but made mistakes and sometimes gave it too much. I know I can learn and improve, starting with my time trialling ability to attack on climbs.
Best of the rest
France have not had a home winner since Bernard Hinault's record-equalling fifth victory in 1985.
Thibaut Pinot and Romain Bardet are the biggest hopes this year. Both are comfortable in the mountains but will seek to limit losses on the time trials. Podium finishes are not out of the question but the top step may just be beyond reach.
Fellow Frenchman Pierre Rolland is an accomplished climber and has switched to Cannondale to further his Grand Tour ambitions. He has ridden more than 2,000km on his time trial bike in the off season - but will it pay off?
Australia's Richie Porte was in the Team Sky squad that helped Wiggins win in 2012 and Froome a year later.
The 31-year-old had a tilt two years ago after Froome crashed out but struggled in the mountains after falling ill.
Porte, who switched to BMC Racing for this year, said: "I've never been in as good shape and, more importantly, I've never been on a team where I've got my own opportunities."
American Tejay van Garderen is also in the BMC squad. He claims sickness ruined his race last year when he was forced to abandon from third place on stage 17.
The British challenge
There are eight British riders in the race and three will be supporting Froome's challenge in the nine-man Team Sky squad.
Geraint Thomas will again play a key role in the mountains, while Ian Stannard and Luke Rowe will do a lot of work on the flatter stages to keep Froome near the front of the peloton and away from crashes.
Mark Cavendish will be going for wins on the flatter sprint-friendly stages. He has won 26 Tour de France stages and needs just two more to equal Hinault's haul. Belgium's five-time Tour winner Eddy Merckx leads the way on 34.
Should the 'Manx Missile' win stage one on Saturday, he will wear the race leader's yellow jersey for the first time.
However, Cavendish says it "was never a career target" to pull on the 'maillot jaune'.
He added: "It's a stage win. The win will get you the yellow jersey. You can only look at it like that. How else will you get the yellow jersey? Even if it was the seventh stage, we'd go into it with the same strategy."
Steve Cummings, who won a Tour stage last year, is also in Cavendish's Dimension Data squad.
Climbing specialist Adam Yates, 23, will ride for Orica-BikeExchange and look to improve on his 50th-place finish last year, while New Zealand-born sprinter Daniel McLay, 24, is making his Tour debut for the Fortuneo - Vital Concept team.
What else should I look out for?
The Tour de France is not all about winning the yellow jersey. The battles for the green points and polka dot King of the Mountains jerseys can be just as intense.
Slovakia's Peter Sagan is chasing a fifth successive points title. Historically the race for green has been the domain of the sprinter but since Cavendish won in 2011, Sagan, who can climb and sprint, has been imperious by picking up points on hillier stages.
Points are awarded at the end of all stages but are stacked in favour of the sprinters on flat stages. There are also intermediate sprints to keep the quick men interested in the mountains.
Froome won the King of the Mountains title last year, more as a by-product of winning the race. The 2014 winner Rafal Majka is a team-mate of Contador, highlighting the strength of Tinkoff's squad.
The harder the ascent, the more points are on offer, with double points at summit finishes. Expect the likes of Bardet, Pinot and Rolland to be interested, particularly if the hopes of a first French winner in 31 years evaporates again.
How can I follow the race?
There will be live text commentary of every stage, with live commentary of the closing 90 minutes of every stage on BBC Radio 5 live Sports Extra or the BBC Sport website.