From the car park at Puerto de Navacerrada the best option is to take the asphalted road (snowy in winter but just as obvious) that winds its way up to the Alto de las Guarramillas (2,268 m.), popularly known as the Bola del Mundo, on the Madrid side. To do this we have to overcome an initial difference in altitude of 408m. (in normal conditions it can take 1h 15'). From here, head northeast and follow the ridge, descending first to the Guarramillas pass (2,159 m) and then ascending to the Valdemartín hill (2,278 m), which should be reached in about 30 minutes from the top of Guarramillas (1 hour and 45 minutes from the start). From this privileged vantage point we have to descend again to the pass of the same name (2,151 m.) and immediately begin the final ascent to the Cabeza de Hierro Menor (2,299 m.), where this excursion ends (40' from Valdemartín, total 2h 45'). The descent to Puerto de Navacerrada is by the same route.