MONT DU CHAT, France — A white-haired man was dancing naked in the middle of the mountain road, his sunburned body rocking imprecisely to a pop song pounding from a set of speakers. His halfhearted attempt to cover himself with one hand as he swayed was mostly ineffectual, which only made his friends laugh harder and cover their eyes. Behind them was a 20-foot-long, homemade banner that read, “VIVE LE TOUR.”

It was late Saturday afternoon on Mont du Chat, a full 24 hours before the competitors of the Tour de France would ascend these brutally steep roads. But the merrymaking, as the man’s striptease made clear, was already in full swing.

For connoisseurs of cycling, mountain roads provide an optimal vantage point to see a race in person. On flat pavement, riders speed past in a thick pack, gone in a flash. On steep climbs, though, they lumber past, often slowly enough for fans to talk to them or touch them or even run alongside them for a bit.

But reaching these roads is no easy task. Prime spots tend to be up several miles of winding pavement, on windswept outcroppings of rock, or, as here in the western edge of the Alps, cut out of thick woods. Local authorities tend to close mountain access roads in the days before the Tour passes through. There is a longtime tradition, then, of cycling fans camping out in the mountains for days, or even weeks, to claim a coveted place along the course.