Spain's Benat Intxausti sprinted to victory in a thrilling finale to stage 16 of the Giro d'Italia as Vincenzo Nibali retained his overall lead with another flawless performance.
The peloton was blown apart on the second of the day's two categorised climbs and an elite group of just 15 general classification contenders fought out a compelling battle on the subsequent descent to the finish line.
After a flurry of attacks, Intxausti (Movistar) managed to break clear alongside three other riders and then produced a decisive burst of speed on the home straight to beat Tanel Kangert (Astana) into second and Przemyslaw Niemiec (Lampre-Merida) into third.
Nibali (Astana), Cadel Evans (BMC) and Rigoberto Uran (Team Sky) all followed in the rest of the breakaway group, 14 seconds later, to remain the top three overall, but Mauro Santambrogio (Vini Fantini) fell from fourth to sixth after being dropped on the climb and losing over two minutes.
Intxausti, who wore the leader's maglia rosa earlier in the Giro, said afterwards: "It seemed like the least appropriate day for me, because the break had huge chances to make it to the finish, and that makes it even more beautiful and special.
"I kept my mind cold in the final kilometre and left all responsibility to Niemiec, so the Astana rider [Kangert] could get on his wheel. I saw them glancing for a bit with 250m to go and didn't wait, jumped from the left side, and it all went well."
Stage 16 took the riders on long and testing 239km route east from Valloire to Ivrea over two categorised climbs.
The day started with the race's second ascent of the category-one Col du Mont Cenis in France and ended with the testing 6km, category-three climb to Andrate, which averages eight per cent in gradient and summitted 17.5km from the finish.
Sixteen riders broke clear of the peloton after 46km and another six men later bridged across to form a group of 22. However, with Cannondale's Damiano Caruso among them and just 9min 57sec down in the general classification, they were only allowed to build a maximum gap of five minutes and the chance of a breakaway winner was lost.
When RadioShack-Leopard upped the pace on the front of the peloton and reduced the deficit to under three minutes, the breakaway riders began attacking each other in a bid to form new groups and reopen the advantage.
Several went clear and momentarily opened up gaps, but one by one they were reeled back in and the last of the groups were caught on the climb to Andrate.
In the peloton, Scarponi attacked midway up the ascent and Nibali quickly followed as they reduced an already thinned-down bunch to just 15 leaders, with only Santambrogio absent among the big names. Mark Cavendish, celebrating his 28th birthday, was also dropped.
Carlos Betancur (Ag2r-La Mondiale) attacked over the summit of the climb and was joined by Samuel Sanchez (Euskaltel-Euskadi) on the tight road down the other side to form a lead duo, but Nibali hauled them back with a virtuoso piece of descending and the rest of the group followed in his slipstream.
The attacking resumed on the flat run to the finish, and after several riders tried and failed to pull away, Kangert, Intxausti, Niemiec and Robert Gesink (Blanco) finally made a move stick and held on to the line.
Stage 16 result
1 Benat Intxuasti (Spa) Movistar, 5:52:48
2 Tanel Kangert (Est) Astana, same time
3 Przemyslaw Niemiec (Pol) Lampre-Merida, st
4 Ramunas Navardauskas (Lit) Garmin-Sharp, +14secs
5 Cadel Evans (Aus) BMC, st
6 Franco Pellizotti (Ita) Androni-Venezuela, st
7 Michele Scarponi (Ita) Lampre-Merida, st
8 Rafal Majka (Pol) Saxo-Tinkoff, st
9 Jose Herrada (Spa) Movistar, st
10 Carlos Betancur (Col) Ag2r-La Mondiale, st
1 Vincenzo Nibali (Ita) Astana, 67:55:36
2 Cadel Evans (Aus) BMC, +1:26
3 Rigoberto Uran (Col) Team Sky, +2:46
4 Michele Scarponi (Ita) Lampre-Merida, +3:53
5 Przemyslaw Niemiec (Pol) Lampre-Merida, 4:13
6 Mauro Santambrogio (Ita) Vini Fantini, +4:57
7 Carlos Betancur (Col) Ag2r-La Mondiale, +5:15
8 Rafal Majka (Pol) Saxo-Tinkoff, +5:20
9 Benat Intxausti (Spa) Movistar, +5:47
10 Domenico Pozzovivo (Ita) Ag2r-La Mondiale, +7:34
Red (points classification) - Mark Cavendish (Omega Pharma - Quick-Step)
Blue (mountains classification) - Stefano Pirazzi (Bardiani Valvole - CSF Inox)
White (best young rider) - Carlos Betancur (Ag2r-La Mondiale)