The Roman road to the Puerto de la Fuenfría from Cercedilla

Start at the Valle de la Fuenfría visitor centre, at km 2 of the Las Dehesas road (M-966) in Cercedilla. The Sierra de Guadarrama National Park's route PNSG_036, the Calzada Romana, follows a track whose first stretch runs more or less parallel to the Las Dehesas road, crosses the Arroyo Pedregoso, passes the Puente del Descalzo and the Pradera de los Corralillos and ends at the Puerto de la Fuenfría, the route's high point at 1,792 m. Return the same way.

It is 9.3 km there and back with 485 m of ascent; allow about 3¾ hours. The park gives the route as 5.5 km one way, 2 h 50, 528 m of ascent, graded beginner, with a high point of 1,792 m; ours is 4.7 km each way. The Comunidad de Madrid's page for the Calzada borbónica, a separate route to the same pass that starts at the Majavilán car parks, gives 2.9 km one way, with 406 m of ascent; the park lists the Calzada Borbónica (PNSG_019) as a separate route too. The grade is Moderate on our count.

The park says parts of the route cross stone slabs, recommends refilling water at the Majavilán fountain, and says that, because the route reaches 1,792 m, in unfavourable conditions it may not be advisable with snow or ice. Pets must be on a lead, and fires, gas stoves and drones are not allowed.

The park's page for the visitor centre gives its opening as every day from 9:00 to 19:00 from April to October and from 9:00 to 16:30 from January to March, November and December, and says the small car park at the centre has a maximum stay of 10 minutes. It lists bus lines 684 (from Madrid Moncloa) and 680 (from Collado Villalba) to Cercedilla, an interurban bus with a stop in front of the centre, and Cercanías C-8 and the Segovia train to Cercedilla; the page says the C-9 is temporarily closed for works.

Route drawn by Global Adventurer along OpenStreetMap paths (© OpenStreetMap contributors, ODbL), with figures worked out from it. Check the forecast and the ground on the day: paths change.