Spain doesn't have long Alpine passes, but rather short, steep climbs—so-called “muros” with gradients exceeding 10 percent. This rewards explosive acceleration and makes the Vuelta the most climbing-intensive of the three Grand Tours.
Then there's the heat. As the only major stage race in late summer, the Vuelta regularly sees temperatures exceeding 35 degrees, and riders who struggle with the heat rarely lose on the climbs—they tend to falter in the third week.
Because it wraps up the Grand Tour calendar, the field is different as well: riders who fell short in the Tour looking to redeem themselves, or young pros in their first role as team leaders. And since time trial kilometers are scarce, seconds—not minutes—make the difference on the climbs. The general classification often remains tight right up until the final week.