British Sky duo Bradley Wiggins and Chris Froome (Sky) face their biggest obstacle en route to a top finish in Madrid in the 2011 Vuelta a Espana today: the Angliru.
Compared by many to the Zoncolan, the Spanish climb is probably not as hard, but there aren't many others out there in western Europe as unremittingly steep, anyway, and it is certainly the most difficult single climb in Spain.
With a maximum gradient of 23.6 percent, and rising 1,245 metres in its 12.8 kilometres, the Angliru has always had a huge influence on the race.
In 2008, Alberto Contador (Saxo Bank) distanced then team-mate Levi Leipheimer - whom Contador now describes as his maximum rival for the Vuelta, although they supposedely were supporting each other back then - by nearly a minute, deciding the Vuelta in his favour. The same happened in 2000 with Roberto Heras, third at the top and first in Madrid.
There are other factors, like the rain, which tends to turn the descent of the previous first category Cordal climb into a skating rink. David Millar's protest in 2002 at the dangerous conditions prior to the Angliru - crashing at least twice, then riding, battered and bloodied, up the climb only to abandon at the top - is still widely recalled.
The weather midday Sunday was overcast and damp, but not actually raining and with no wind. In Asturias, though, one of Spain's wettest regions, that is no guarantee there won't be a downpour soon - or the sun might break through. We'll see.
Prior to the stage Wiggins his closest rivals are the little-known Bauke Mollema (Rabobank), just 23 but already a leader of the Vuelta for one day on the Covatilla and just 36 seconds and the slightly better known (but only slightly) Juan Jose Cobo, fourth at 55 seconds.
Cobo - Wiggins strongest rival on the Farrapona - is something of an enigma: 30 years old and a pro with Saunier Duval, then Geox for most of his career, his first 15 minutes of fame came when he took a crushing but unexpected victory in the Tour of the Basque Country in 2007.
The following year, 2008, Cobo ‘inherited' a victory in the Tour after team-mate Leonardo Piepoli tested positive in the Pyrenees. The winner of a Vuelta stage in 2009 through the sierras of Madrid, this year Cobo has had a difficult season, and mid-way through was thinking of abandoning the sport.
After changing his mind, in the Tour of Burgos, however, he was back in good shape and third overall, and is now the best-placed Spaniard in the country's biggest bike race.
Will this stage decide the Vuelta? Probably but not definitely. In 2002, the leader at the top, Roberto Heras, was edged out by Aitor Gonzalez in the finish, and in 1999 Abraham Olano led before and after the Angliru, but his crash on the Cordal and subsequent broken rib forced him to quit a few days later in the Pyrenees.
If the time gaps are not huge, then the ascent to Peña Cabarga on Wednesday - where Nibali took the lead in last year's race, but then lost it to Joaquim Rodriguez the following day - will be crucial.
Support for Cobo, assuming he doesn't crack today too, will be huge, given Peña Cabarga in the middle of his home region, Cantabria. On top of that, there are still time bonuses for each stage, right the way through to Madrid. Either way we will have a lot clearer picture of the overall by Sunday evening and a much needed second rest day on Monday.
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