Tagus: from Fuente García to the canyon

The Tagus rises in the Montes Universales, in a mountain range exceeding 1,800 metres. A trickle of water springs from Fuente García, within the territory of Frías de Albarracín, gathering other mountain springs to reach the Monument to the Source, sculpted by José Gonzalvo Vives in 1974, which pays tribute to Teruel, Cuenca, and Guadalajara. It lies outside the Natural Park, in Teruel province.

Its first bridge inside the Park is the Puente de las Tres Provincias, or Valdeminguete bridge, precisely on the border between Guadalajara, Cuenca, and Teruel. Upstream, surface flow can dry up in summer; from this point onward water runs year-round. It remains a modest mountain stream, locally called the Tajillo, until joined at Las Juntas by the Hoz Seca. A local saying runs: «The Tagus bears the fame, while the Hoz Seca bears the water».

Downstream, the river carves deep canyons. At Peralejos de las Truchas, the Puente del Martinete is the first substantial stone bridge across an already voluminous Tagus. Further down it cascades over the Salto de Poveda waterfall and, beside the Puente de San Pedro, receives the Gallo: after heavy rain, the Gallo runs reddish with eroded Triassic clay while the Tagus runs milky with kaolin silt, the river flowing with two distinct colours for several hundred metres.

Between Armallones and Ocentejo, at El Hundido, a massive 16th-century rockfall dammed the river: in 1578 Ocentejo residents petitioned King Philip II for disaster relief. At Valtablado del Río, at about 840 metres altitude, the Tagus is wide and deep, flowing with stronger current than it appears, passing under the GU-929 road bridge by a poplar grove. The atlas follows the river to this point; the Tagus continues onward toward Entrepeñas reservoir.