The loop starts and ends in Torrelaguna. It first heads to Patones and climbs narrow, twisting roads to El Atazar, with the dam and the reservoir in view from several points.
It then goes round the reservoir through Cervera de Buitrago, Robledillo de la Jara and Berzosa del Lozoya, passes Puentes Viejas and Lozoyuela-Navas-Sieteiglesias and returns to Torrelaguna via El Berrueco. This is the quietest part of the Madrid Sierra Norte, with small villages and little traffic.
It is about 102 km and just over three hours without stops, with some 275 bends and two hairpins. Altitude ranges from about 700 m to 1,100 m. The reservoir roads are narrow with no hard shoulder: at weekends there are cars stopped at the viewpoints.