From Rascafría (El Paular) to the Puerto de Cotos it’s 9.4 miles (15.1 km) at an average of 4.6%: 2,260 ft (689 m) of climbing, from 3,743 to 6,004 ft (1,141 to 1,830 m). It’s a gentle, steady climb with no double-digit ramps, ideal for putting in miles at a steady pace or for riders just getting into long climbs.
What the climb is like
You climb on the M-604, which leaves the Lozoya valley and enters the pine forest. The grade barely changes: 4-6% almost the whole way, with the steepest stretches (around 8%) near the end. The pavement is very good. At the pass are the Venta Marcelino and a Sierra de Guadarrama National Park visitor center; the road continues toward the Puerto de Navacerrada, and the access road to the Valdesquí ski area branches off here.
A note on the numbers
The elevation gain and summit elevation match across all sources (2,211-2,270 ft / 674-692 m and 5,994-6,004 ft / 1,827-1,830 m), but the length depends on where you start: CyclingCols measures from the center of Rascafría (10 miles / 16.1 km at 4.2%), Climbfinder gives 9.4 miles (15.1 km) at 4.6% and altimetrias.net, from the El Paular monastery, 8.5 miles (13.6 km) at 4.9%. We use the middle figure. We don’t publish a section-by-section profile.
Its Vuelta a España history
Cotos has featured about 20 times in the Vuelta since 1974. Riders first over the top include Marino Lejarreta (1980), Richard Virenque (1998), Sergio Higuita (2019) and Richard Carapaz (2022), who won the stage at the Puerto de Navacerrada that same day.
When to go, water and traffic
At 6,004 ft (1,830 m), the road can have snow and ice in winter; people go sledding in the meadow at the pass. From spring to fall it’s a very pleasant climb. There are fountains in Rascafría, next to the visitor center, and at the Venta Marcelino. Traffic picks up on weekends, especially when there’s snow.
What gearing to use
A 34x25 or 34x28 is more than enough. At 3 W/kg (watts per kilo of body weight) and 159 lb (72 kg), you’ll ride about 8.7 mph (14 km/h) on 6%, and with a 34x28 that’s 90 rpm. It’s a good climb for practicing a high cadence. Compare your gearing in the calculator.
Tips
- Use it for pacing practice: 50-60 minutes of steady effort with no sudden changes in grade.
- Link it with Navacerrada and La Morcuera for a classic loop around the Lozoya valley.
- Bring a windbreaker: it’s usually windy at the pass.
Frequently asked questions
How long does it take to climb the Puerto de Cotos from Rascafría?
A 159 lb (72 kg) rider on a 21 lb (9.5 kg) bike takes about 54 min at 3 W/kg (216 W), 1 h 03 min at 2.5 W/kg and 43 min at 4 W/kg. Work out your own time with your weight and power in the calculator on this page.
Is the Puerto de Cotos hard?
It's one of the most manageable climbs in the Sierra de Guadarrama: a 4.6% average and maximum ramps of around 8%. The hard part is the length, 9.4 miles (15 km).
Where can you get water on the way up to Cotos?
In Rascafría, next to the visitor center, and at the Venta Marcelino, at the pass.