Defending champion Jonas Vingegaard leads the Tour de France out of the Basque port of Bilbao on Saturday on a 21-day adventure crammed with peaks, postcard panoramas and an eye-catching showdown on a massive dormant volcano on the 3,404km route to Paris.

The 30 mountains on the route lend Vingegaard of Jumbo-Visma an edge over two-time champion Tadej Pogacar backed by a reinforced Team UAE squad.

A year ago, Jumbo's collective strength helped the Dane, more resilient on the toughest climbs, outlast the daring Pogacar in a ruthless war of attrition in the mountains.

Pogacar had finished first the year before with Vingegaard second. This promises to be their third heavyweight bout.

Pogacar won the Slovenian national championship on Sunday and said it was a good test of his legs ahead of the Tour.

"I'm happy to have succeeded. It was a good test before the Tour. My legs were pretty solid," said Pogacar.

"Now I'm going to rest before heading to Bilbao for the start."

French hope Romain Bardet said: "It will be a beautiful battle, especially if they are both at 100 percent.

"There's a plethora of pretenders following right behind them."

Tour folklore insists the champion is chosen by the Alps, and 13 of this year's 30 mountains are there, with six more in the Pyrenees, five in the Vosges, four in the Massif Central and one each in the Jura and Basque Country.

The Tour makes a hilly start over the forested slopes around Bilbao and San Sebastian.

The Spanish Basque Country is a cycling heartland and fervent local fans will be out in force for the Grand Depart.

Clever route design has set up what promises to be a swashbuckling struggle over the first three stages in an event televised in 190 countries.

The opener, around the Bilbao back-country, is laced with terrain to tempt the one-day mavericks to go for glory with Frenchman Julian Alaphilippe one to watch.

The 20km descent to the chic coastal resort of San Sebastian on stage two might raise an eyebrow or two after the shocking recent death of Swiss rider Gino Maeder at the Tour of Switzerland.

The peloton enters France on day three and then swings west for two stages through the Pyrenees before heading back up the Atlantic coast.

The vineyards of Bordeaux, on stage seven, serve as an aperitif to the star landmark of this Tour, the magnificent dormant volcano at Puy de Dome.

The ascent provides a spectacular view of the dormant domes along central France's tectonic faultline.

Neither fans nor vehicles will be allowed on Puy de Dome's stark, steep upper reaches where pretenders will be brutally exposed to the elements.

Another potential decider is stage 17 from Mont-Blanc, which climbs four peaks, the last into the rarefied air above the tree line at the 2,300m summit of the final climb to Courchevel, where 2019 champion Egan Bernal may once again deliver a late challenge.

Gone is the day-20 individual time-trial that made recent finales something of a lottery. Instead, the last stage before Paris offers another five mountains and no let up for the leader.

As usual the Tour is rich in sub-plots.

Rising star Biniam Girmay is fully capable of becoming the first black African to win a stage on this 110th edition.

"It's a big moment for me and for Eritrea," the 23-year-old leader of Belgian team Intermarche-Wanty said.

Targeting the sprints, Girmay faces veteran British speed king Mark Cavendish, who hopes to break a tie with all-time great Eddy Merckx with a 35th Tour de France stage win.

The Tour ends with the traditional mass bunch sprint on the cobbled Champs Elysees on July 24 with the trophies then distributed beneath the Arc de Triomphe. In 2024 the finish will be in Nice because of the Paris Olympics.

The route of women's Tour de France, from July 23-30, was unveiled on Thursday with a 1,000km itinerary starting from Clermont Ferrand and taking the riders through the south and an ascent of the Col du Tourmalet in the Pyrenees as its highlight.