Britain's Chris Froome has called the route for the 107th edition of the Tour de France "brutal" as he aims for a record-equalling fifth title.
Riders will face 29 mountains on the 3,470km (2,156-mile) 21-stage route, which starts in Nice on 27 June.
Froome's hopes may rest on the mountain time trial at La Planche des Belles Filles before the traditional final sprint stage in Paris on 19 July.
"It will be won and lost in the mountains but that suits me," he said.
Jacques Anquetil, Eddy Merckx, Bernard Hinault and Miguel Indurain are all five-time winners of the race, with Froome one behind after successes in 2013, 2015, 2016 and 2017.
"That is really the hardest route I've seen anywhere in the past five years," added Froome who missed the 2019 Tour after a high-speed crash before stage four of the Criterium du Dauphine in June.
"There are loads of opportunities for the general classification to play out and the main rivals to go head to head. That's what everyone wants to see."
The Tour, which begins a week early to accommodate the Tokyo Olympics starting on 24 July, features five summit finishes - one of them being the time trial at La Planche des Belles Filles - and is likely to favour the climbers.
"It will be physically challenging throughout," said race director Christian Prudhomme.
"Even the so-called flat stages will be very tough for the pure sprinters. There are traps everywhere along the route."
A route for the climbers
The 2020 Tour boasts one of the most challenging opening weeks in recent editions of the race.
Two stages start and finish in Nice, the second of which involves almost 3,700 metres of climbing over the Col de la Colmiane, Col de Turini and Col d'Eze.
The race then heads south west through the Massif Central, with summit finishes on Orcieres-Merlette on stage five and Mont Aigoual.
Colombian champion Egan Bernal and his Ineos team-mate Froome will expect to challenge, as will France's Thibaut Pinot.
A thigh injury saw Pinot, 29, withdraw on a dramatic stage 19 to Tignes on the 2019 Tour while in fifth place.
The Groupama-FDJ team leader had hoped to become the first French winner of the yellow jersey for 34 years.
Froome, 34, is only just about to return to cycling after suffering a catalogue of injuries which included a fractured right femur, a fractured elbow and fractured ribs.
Julian Alaphilippe, who led the 2019 edition of the Tour for 14 stages before finishing fifth overall will also be buoyed by the omission of both Alpe d'Huez and Mont Ventoux next summer and by a route containing only two stages in the Pyrenees.
The race against the clock on the 36km (22-mile) stage 20 to La Planche des Belles Filles, with the final 8km (five miles) all uphill, could prove decisive though.
Stage six of the 2019 Tour finished on the mountain with Dylan Teuns taking the stage victory as Alaphilippe lost the yellow jersey, temporarily, to Italy's Giulio Ciccone, while 2018 Tour winner Geraint Thomas put in an impressive late attack.
Froome won stage seven on the mountain in 2012, while playing the role of a super-domestique as Bradley Wiggins became the first Briton to win the Tour.
La Course returns to Paris
Tour de France organisers ASO also announced that women's one-day race La Course will return to Paris next year in the format of its first three editions.
The women's peloton will race 13 laps of a circuit around the Champs-Elysees, completing 90km in total, with the race currently scheduled for 10 July, while the final stage of the men's Tour in Paris is on 19 July.
After three years in Paris following La Course's first edition in 2014, the race moved to a two-day event in 2017 before becoming a single mountain stage in 2018 and then a hilly one-day race in Pau this year.
Dutch rider Marianne Vos is the reigning champion, having also won La Course's inaugural edition.