Puy Mary (France)
The slow-burning fight for the Tour de France's yellow jersey erupted in earnest on the remains of a once-giant volcano on Friday, with race leader Primoz Roglic using its punishing slopes to grow his overall lead.
One of the big losers of the day was Egan Bernal, last year's champion from Colombia who was unable to match Roglic's pace on the arduous ascent of the Puy Mary.
Bernal tumbled from second to third in the overall standings and slumped exhausted across his handlebars at the top.
Tadej Pogacar, the only rider able to stay with Roglic on the last climb, vaulted to second overall. He trails Roglic by 44 seconds.
Bernal fell back to 59 seconds behind Roglic, the winner of last year's Spanish Vuelta who is increasingly looking the firm favorite to win in Paris in eight days.
The intense stage, one of this race's hardest with seven ascents of note, was won by Colombian rider Daniel Martinez. He had been part of a breakaway of lower-order riders.
German rider Lennard Kämna was second on the climb up the Puy Mary.
The 191-kilometer (119-mile) trek through the hills and mountains of the Massif Central range was one of the toughest of this Tour, with the greatest total elevation gain of any stage - a whopping 4,400 meters of climbing in all.
The effort was written large on the face of Bernal and other riders as they slowly lost contact with Roglic on the last climb, rearing upward with gradients of 15 per cent.
The Slovenian described it as a "hard climb" but made it look easy, showing how hard it will be for rivals to wrest the yellow jersey from his shoulders in the last week.
"Every day is closer and closer to the end," he said.
At the start of Stage 13, just 1 minute, 42 seconds separated Roglic and 10th-placed Spanish rider Mikel Landa - the smallest Stage 13 gap between the top 10 of any Tour since World War II. But that all changed on the road.
French riders Guillaume Martin and Romain Bardet, who had been third and fourth overall, respectively, both tumbled out of the top 10.
Bardet was hindered by a mid-stage crash that also took down Dutch rider Bauke Mollema, who had been 13th. Bardet scraped himself off the tarmac and carried on but an injury to Mollema forced him to abandon what had been his tenth Tour.
The riders will have no respite in the coming weekend of climbing ahead of the second and last rest-day on Monday, when all racers and team staff will be tested again for COVID-19.
Saturday's lumpy Stage 14 with one mountain pass, multiple hills and a downhill finish to the gastronomic city of Lyon isn't likely to shake up the top order. Top contenders will be bracing instead for a very tough uphill finish on Stage 15 on Sunday.
Sunday's long and winding ascent of the Grand Colombier in the Jura mountains, one of five ranges scaled by this Tour, could again shake up rankings.