The road to the port of Navacerrada, formerly called the port of Mançanares since the 13th century, which came to have a medieval inn with privileges and passage concessions by order of King Alfonso X, began to be built in 1778, during the reign of Carlos III, costing one million reais for each league of road. To amortize the work, a portazgo payment was established that had to be paid in the old Casa del Portazgo, where the Fonda Real is now located. Transit through the port posed a risk due to inclement weather, the state of the pavement and the assault of bandits, who took advantage of blizzards and cart accidents to rob travelers.
In 1832 an optical telegraph line was inaugurated between Madrid and La Granja de San Ildefonso, through a daring system of towers and visual signal codes that transmitted messages between the towns of Madrid and the palaces of La Granja and Riofrío. One of the towers was installed on the Alto del Telégrafo, it had three floors and an entrance located several meters above the ground, with access via a ladder, to prevent the entry of criminals and not be isolated by snow storms, which in At that time they isolated the mountains for five months a year. The line stopped working right away, in 1838, and over time the communications tower became a forest fire surveillance post and sometimes to report an accident, such as the one suffered by King Alfonso XII when his cart overturned in one of the the Seven Revolts.