(S) Start from the Public Car Park in Torrelaguna (C/ Marqués de Torrelaguna). Turn left along Paseo de la Varguilla and through the archway. Turn right into Traversía La Plaza and right again into the cul-de-sac of the C/ Juan de Gamarra to see the Portada de los Quiros. Return to the Traversía La Plaza and turn right to enter the Plaza Mayor where you will find the Town Hall and the church dedicated to Santa María Magdalena.
(1) Moving on, to the right of the church along the C/ Cardenal Cisneros and C/ Montera our route passes the Casa Solariegos in the picturesque Plaza Montero. Heading down some steps to the stream Arroyo Matachivos, we pass a tower on the left, Torre de la Montera. The Torrelaguna wall is now in quite a bad state.
(2) Turn left along the stream (most of the year dry, as the main flow of water is channeled underneath the cement) to reach the curved bridge Puente Marichivas. Crossing the bridge, bear left along C/ Opranilla to reach the Fuente Gorda. Take the slope that rises behind the fountain, along C/ Juan del Campo then right along C/ Real de los Merinos to reach the Fuente de los Merinos. Turn left to go along the Salida de San Andrés with the high wall on the left. Follow this street, ignoring all exits to the right and cross straight over the C/ del Canal Isabell II, continuing out of the village along C/ del Montero. The track bears right and carries on for some time through cultivated fields with olive trees and a whole collection of wild plants, including rosemary, lavender, thyme, olive and almond trees, rock rose, and esparto. Don't be drawn down to the main road but keep more or less parallel with it until reaching an obvious track with grey stone covering, one of many service roads for the Canal Isabel II infrastructure. Torrelaguna and this whole area is marked by the various reservoirs, pipes, pumps, and siphons that have been constructed over the centuries to supply drinking water to Madrid.
(3) Go down the service track for about 100m to reach a T-junction and turn left. The track goes across a bridge over the Arroyo de San Román but our route bears left then drops down to go along the (usually) dry stream, heading into the gorge. The route follows the stream into the limestone surroundings. The path passes under an aqueduct and then goes under a siphon that carries large water pipes. There are a number of constructions, some now derelict, others carrying Madrid's water. At about this point, the geography changes and we begin to see some slate and the stream is now above ground. A little further on our route crosses the GR-10.1 but keeps following the stream, this is the beginning the Senda San Román. Our path twists and winds with the stream, constantly crossing and recrossing the flow of water but without too much difficulty. After about 3km the route reaches the small Tomillares Reservoir , where it crosses the small dam, only wetting our boots a little.
(4) From here, there is a steep climb up towards the road (M-133) but just before reaching the tarmac, take a path off to the left that goes behind a number of bee-hives. This path then drops down to the left next to an old wire fence until a gap opens up on the right and allows us to descend to another small stream. Then it's back up the other side on a zig-zagging path to reach the stream Reguero del Tinado. Cross this and also the next stream Arroyo de las Tejeras. Logic suggests (and tired legs implore) that we head over to the Atalaya by a path that joins a dirt track further up the hill. However, our route descends slightly to reach the stream Vallejo Ancho where the route bears right to go up by the stream to reach the Fuente Atalaya. Follow the path, well-trodden by the cows and other livestock, to reach a dirt track and a short climb up to the Atalaya Torrepedrera.
(5) Once the Atalaya has been inspected (access by a metal ladder allows visitors to enjoy the views from the top) and the vistas over the largest reservoir in the district, the Embalse Atazar, that traps the waters of the Lozoya River, our route returns to a southerly direction, going right along the dirt track crossed earlier. Look out for the Fuente Pedro Arias on the right just off the track, before reaching a metal gate that leads out onto a road at a small roundabout. This is the entrance to a housing estate known as Los Tomillares.
(6) Turn left and climb up the steep road that runs parallel with the border between Torremocha (the housing estate is in that part) and Torrelaguna. Then straight on, to go down past a house and continue along a dirt track to reach the valley floor. Here, turn right to follow the stream with a pine forest on the left. Keep straight on as the main track swings left up the hill. Stay left of the stream, on the Senda Arroyo, for about 1km to pass an old well or water intake access point. Just a bit further on, the path crosses the stream and follows a concelled canal or irrigation ditch. Keep bearing left with the stream to see Torrelaguna down in the distance. The path comes out onto a dirt track that leads to the bottom of the valley. Take the track that leads diagonally up to the left to reach the old road between Torrelaguna and El Berrueco. This goes past the Canal Isabel II large pipes coming down from the east and shooting up to the west, then reaches the aqueduct Matachivas.
(7) Don't join the road but head down by the side of the stream to reach the first houses of Torrelaguna. Shortly, on the left, go past the hermitage dedicated to San Esteban (or San Sebastian) and carry straight on along the C/ San Sebastian into the village. Just before reaching the Puente Marichivas, turn right into C/ de la Redondilla until the Post Office (Correos) comes into view. Bear left along C/ Almendro to see the Pino Centenario (100+ years old pine tree). Continue on up the C/ Pino Centenario to reach the Plaza del Poeta Juan de Mena. Carry straight on to reach the Plaza Mayor once more. Bear left, past the Bar La Plaza to go along C/ del Cardenal Cisneros to the crossroads and the old Casa Patata. On the opposite corner is the Palacio Arteaga. Turn right then left to enter the C/ de la Marquesa de Torrelaguna and back to the Public Car Park.(E)