Geraint Thomas has boosted his bid to become the Giro d'Italia's oldest winner by moving back into the leader's pink jersey  after the race exploded into life at the start of a dramatic and decisive final week in the Dolomites.

Joao Almeida (UAE Team Emirates) won the tough 16th stage atop Monte Bondone for his first victory in a Grand Tour. The Portuguese cyclist crossed the summit finish just ahead of Thomas, who also picked up valuable bonus seconds.

Primoz Roglic (Jumbo-Visma) was third 25 seconds further behind.

Tuesday's result meant Thomas (Ineos Grenadiers) moved back into the lead, 18 seconds ahead of Almeida and 29 in front of Roglic.

Jack Haig (Bahrain Victorious) was Australia's best finisher, coming in 17th, 4:15 behind to leave him 18th overall, 10:58 adrift.

Thomas turns 37 on Thursday, three days before the race ends in Rome. The oldest Giro winner is Fiorenzo Magni, who was 34 when he won in 1955.

Tuesday marked the beginning of a brutal final week. It was one of three of the last six stages that have been given the maximum difficulty rating of five stars.

There was more than 5,000m of elevation and five categorised climbs along the 203 km route from Sabbio Chiese, including the top-category climb to the finish.

And it was on that climb to Monte Bondone that the race sparked into life.

Almeida attacked with less than seven kilometers remaining and Thomas made his move shortly after, bridging across to set up the battle for the stage win. Primoz, who had been in the leading group, could not go with him.

"A special victory, a dream come true," said Almeida, who climbed to second in the overall standings.

"I worked together with Thomas to put seconds between us and Roglic, but then my main goal was the stage win. I try to improve day by day to become the best version of myself."

"It was a very tough day, a lot of climbs," Thomas said. "I am happy with how it went. I found myself in front with Almeida, he was better in the sprint.

"I am not surprised by him, he is a very strong rider and a strong pretender for the maglia rosa."

Wednesday's 17th stage offers a brief respite as the 195 km route from Pergine Valsugana to Caorle starts with a gradual descent before a long, flat finish which is likely to end in a bunch sprint.