By David Sharp
BBC Sport on L'Alpe d'Huez
Without warning, just past the picturesque Alpine village of Bourg d'Oisans the road suddenly rises.
Some fans got more carried away than others
I wheel the car round and up to the right and realise I have entered hallowed ground.
Here begins a road that helter skelters its way 1860m above sea-level to the out-of-season ski resort of L'Alpe d'Huez - the most renowned of all Tour de France mountain-top finishes.
Once you are on the incline there is no turning back.
The gradient is frightening - on the map it looks like a piece of string thrown across the mountainside.
Weaving past scattered groups of enthusiastic amateurs tackling the route ahead of their heroes, I observe the build-up of spectators gathering on the roadside verges.
I pass a rabble of rampant orange-clad Dutch fans dressed as boy scouts wearing huge cartoon clogs
A melting pot of nationalities jostle for prime parking spots for their cars and caravanettes.
Beers are already being cracked open, picnic tables appear on grassy slopes and throngs of fans head up the mountain on foot as if on some kind of pilgrimage.
Since Alpe d'Huez was introduced to the Tour de France in 1952 as the first high-altitude city in the race's history, it has seen some of the race's greatest moments.
It is a battleground for superhumans, a Mecca for cycling.
The list of winners at L'Alpe d'Huez reads like a roll of honour of Tour legends.
All nationalities gather on the slopes
Fausto Coppi won the first ever stage here in 1952. Other winners include Bernard Hinault, Marco Pantani and Lance Armstrong.
By the time we head back down the mountain to pick our vantage point just beyond the 5km banner, thousands already hug the road.
I pass a rabble of rampant orange-clad Dutch fans dressed as boy scouts wearing huge cartoon clogs, larging it up, singing and laughing.
A woman is dressed as an angel and explains to me when I quiz her peculiar clobber that she is here in celestial opposition to ubiquitous German eccentric Il Diablo.
Groups of graffiti artists diligently daub their heroes names on the road at various intervals hoping to inspire them to victory or simply survival.
The air is buzzing with anticipation.
Unlike most other sports, the spectator here is free to wander wherever they fancy.
The vast majority of the crowd are respectful enough to keep their distance.
They cheer and clap each rider from the leaders to the "laughing" group bringing up the rear.
Occasionally some unhinged goon will run alongside showering riders with water or giving them a push up the hill but it is mostly high-spirited encouragement.
After hours of noise and anticipation the crowd hushes as the race helicopter appears, hovering above, signalling that the riders have started the fearsome final climb of the day.
Through a gap in the trees to our right we glimpse Iban Mayo gliding towards the hairpin 50 metres down the road from us.
The talented 25-year-old Basque climber is quite literally flying up the mountain. It is a stunning sight and the crowd erupts.
In just over half an hour all the big guns have passed. We turn and trudge back up the mountain as the majority of the crowd stay to cheer on the gallant stragglers.
Every once in a while every sport will throw up a magical moment: a Borg vs McEnroe in 1980; a Manchester United v Bayern Munich in 1999.
Every time it makes it onto the Tour calendar, L'Alpe d'Huez provides a treat worthy of the boast, "I was there".