Stage 20: May 29 2010 - Bormio - Passa del Tonale 178 km

It's 50 years since Imerio Massignan first led the Giro over the immense Gavia and, weather permitting, this classic ascent features as part of the race's most intimidating mountain test. Three major ascents contribute to what is by far the greatest tally of climbing – a staggering 6,320m for the day.

There's a brief passage into Switzerland before the epic 25km rise to 2,618m and the Cima Coppi prize awarded to the first rider over the race's highest summit at the Passo di Gavia. Still to come is the final and surely race-deciding climb on the Passo Tonale.

Procycling's favourite to win:

Winner of two stages last year and back for overall victory this time, Cervélo's Carlos Sastre will relish today's challenge. The dogged Spaniard will be difficult to chase down if he gets a significant advantage on any of the key mountain stages.

Scarponi says:

Stage Details

Distance: 178km
Vertical climb: 6,320m
Highest point: 2,618m
Terrain: High mountain
Category: Road Stage