According to the chronicles, Philip II personally chose these sites to build a monument "that would reveal his power and grandeur to future centuries", due to the great abundance of water, fertility and freshness of the land, the good quality of the berroqueña or granite stone, and proximity to good and abundant pine forests for construction timber" (Valsaín, Guadarrama, Pinares Llanos, El Quejigar and Navaluenga). Let us begin our route to venture into this wonderful natural environment that captivated the monarch.

(1)We leave La Lonja through the Arcos de la Compaña, turn right between Carrero Blanco park and the Mª Cristina University, (next to the park gate we can see one of the magnificent Virginia juniper specimens located inside) and ascend along Conde de Aranda avenue until we reach…

(2)…the Arca del Romeral, (at the foot of the dam of the same name) which collected the channeled waters coming from the Arcas de la Merinera and El Helechal. The dyke of the Presa de El Romeral, built by Juan de Villanueva in the 18th century, suffered a breach in the winter of 1944, simultaneously with the Presa del Batán.

Beside the dam, three steps begin, from which the ascending path emerges (surrounded by sticky rockrose and steppe rockrose) and then gradually separates from the wire fence, always climbing, parallel to the Arroyo del Romeral, leading to a grey spring-loaded gate: at this point, we cross the Cordel del Valle route. Continue ascending in front of the gate until reaching the road. This path continues through a pine forest of black pine, the predominant species in the area, along with Miera juniper, cantueso, botonera…. Do not deviate to the left, confused by the wooden arrows that mark the route to the Arboreto.

(3)Once on the road, straight ahead, the Camino de los Gallegos begins. We will see splendid specimens of Spanish fir and melojo. Along this path, you will have a wonderful view of the ridges of Monte Abantos, whose numerous landslides gave the name in the past to the Arroyo del Cascajal, currently known as the Romeral. We find Montpellier maples, holm oak, gall oak, pedunculate oak, cherry... surrounded by broom and black broom (whose legumes ripen before those of the broom).

About 300 metres to the right, along the road, is the Fuente de La Concha, in whose surroundings we can find species such as fir, chestnut, maple, European spindle, goat willow, birch, osier, almond, buckthorn, ash, poplar, cedar and wild pear.

As we continue our ascent, we come across numerous and magnificent specimens of larch and beech from the reforestation projects carried out by students of the Escuela de Ingenieros de Montes, until its transfer to Madrid in 1914. Also common heather and common juniper. Accompanying them with a herbaceous habit is the beautiful peony. All this together with the predominant species when ascending in altitude, the Scots pine. Shortly before leaving the Camino de los Gallegos, to your right, is the Fuente del Trampalón.

(4)This path will lead us directly to the meadows at the foot of the Puerto de Malagón. We reach the paved track that ascends to this pass. In the clearing of the mountain, you may see on the top of some pine trees the bolsones —winter nests— woven in white silk by a fearsome caterpillar: the pine processionary. After completely eating the needles of the pine tree on which they are located and during the first warm days of spring, the caterpillars leave the pine in procession to find a suitable place underground where they will transform into moths.

We reach the Puerto de Malagón (1,536 m). To the right, the track continues towards Peguerinos and the Puerto de Los Leones. In front of us, the Tobar Reservoir, which supplies water to San Lorenzo via a tunnel that crosses the mountain. Once there, we cross the Paso Finlandés and turn onto a wide track that leads off to the left.

On the sunny slopes, the repopulated pine forest is maintained, while in the rest, the brushland formed by mountain broom and cambroño predominates. On the former species, you may observe small masses of foam; inside them, tiny spittlebugs protect themselves from predators and dehydration. These are insects belonging to the spittlebug family.

As you continue your ascent, you can observe small whitish rocks along the path, originating from a marble outcrop that emerges amidst the gneiss predominant in this area. We follow it until we reach, on the right-hand side, a drinking fountain...

(5)…and the meadows that give rise to the Arroyo del Hornillo (it is the valley parallel to that of the Tobar dam and stream). There is no marked path, but it is hard to get lost as you only need to follow the riverbed which leads directly to the pine forest. Once here, we take a path parallel to the stream, among pines, which leads to a forest track: we follow it for a few metres until it separates from the riverbed, which we cross. At this point, we stop advancing parallel to the stream and move along the hillside, without losing height, following the walls parallel to the stream.

Once again we return to the stream via a fairly steep "street", where we again encounter the pine forest and a small group of poplars. The path reappears on the left bank.

(6)From here, it is only a few minutes to the Cascada del Hornillo. Once reached, descending along its left side, we will arrive at a forest track (already off-route) that leads to a recreational area next to the bridge of the Aceña river, on the road connecting Robledondo with Santa María de La Alameda.