Joaquim Rodriguez became the first Spaniard to win Italy's Tour of Lombardy classic with a gutsy ride in torrential rain on Saturday.
'Purito' attacked in the final part of the Salita di Ello, a 3.25-km ascent at an average gradient of 7.4 percent, and held off a strong chasing group on the flat.
The win gave Rodriguez top spot in the World Tour standings ahead of Britain's Tour de France champion Bradley Wiggins.
Spain's Samuel Sanchez was second and Colombian Rigoberto Uran finished third.
Rodriguez's victory capped a great season for the Katusha rider after he won the Fleche Wallonne in April as well as second place overall in the Giro d'Italia and third in the Tour of Spain.
"This is the most important triumph of my whole career," Rodriguez was quoted as saying in a team statement.
"This was a perfect season. Today I was feeling in great shape: in fact I made my team mates work during all the crucial moments of the race.
"When I saw that all my rivals were tired and I felt so great, I realized I had a great chance to win. To tell the truth I thought that somebody could join me in that attack, but instead nobody could answer and that makes this victory even greater."
As expected, the brutal climb to the Muro di Sormano sorted the men from the boys.
The two-kilometer ascent at an average gradient of some 15 percent blew the peloton apart with Alberto Contador, Vincenzo Nibali and Rodriguez among those setting the pace.
World champion Philippe Gilbert crashed in the descent and pulled out.
"He's got some burns and cuts but nothing serious," his BMC team manager John Lelangue told RAI.
Nibali also hit the deck in the descent from the Madonna del Ghisallo but managed to get back on the bike and rejoin the peloton.
The Italian, one of the pre-race favorites with Contador, Rodriguez and Gilbert, had not fully recovered before the last ascent and did not figure in the finale.