The Roman road of the port of Fuenfría represents the best preserved road section of Roman origin in the Community of Madrid. Since its construction in the 1st century, it has been used for centuries by the peoples of the two plateaus to cross the peaks of the Sierra de Guadarrama, undergoing important improvement and maintenance reforms, such as the reconstruction of the bridges in the Madrid sector in 1728. The construction of an engineering work of such magnitude for the time meant an important environmental alteration in the landscape and an ecological impact on the mountain ecosystems, in the same way that it happens today when designing new roads and highways. At the opening of the roadway box, the Roman engineers ordered to cut down and burn large areas of forest to function and act safely on the ground, adapting the environment to the needs of the road and at the same time working safe from wild animals , especially bears and wolves, who mercilessly attacked the workers from the depths of the forest. The loss of forest masses caused a degradation of plant species, leaving the undergrowth highly exposed to erosion, which, by losing the plant cover, breaks the dynamics of the landscape and increases the risk of landslides in the rainy season and avalanches in winter.