The Fonseca Bridge is a bridge of natural origin located in the municipality of Castellote. It is a fluvio-carstic formation, specifically, a tuff or travertine building generated by the Guadalope River that has originated the tunnel through which it currently runs.
Rivers flowing through limestone rocks dissolve part of the rock causing a large amount of calcium carbonate to concentrate in it. When it becomes saturated or due to changes in environmental conditions, the water is not able to carry as much load, the chemical compound precipitates on the riverbed and the vegetation and animal remains that cover it. This carbonate petrifies the plants of the river and its banks, which, when they die, form the base on which new vegetation develops. In this way, a tuff building is being constructed, which is the name given to this type of rock that grows upwards. There comes a time when it is impossible to grow more and then the river breaks through, cutting the rock and leaving remains of the tuff on the banks. Exceptionally, if the tuff has grown overhanging forming a waterfall and leaving a cave-like hollow, the river seeks its way through it, forming a tunnel.
Inside, humidity conditions are generated that create a microclimate that contrasts with the surrounding environment. Nearby you can find shelters with cave paintings of Levantine Art, declared a World Heritage Site.
How to get there
The Ladruñán – Puente Fonseca trail starts in that neighborhood, passes through the neighborhood of La Algecira (you can also start here) and continues towards the river up to the ford bridge. There it becomes a path that runs along the left bank of the Guadalope up to the natural bridge. The distance is 13 km round trip (11 kms from La Algecira). By off-road car you can access by the track that continues from the ford to the parking lot of El Arenal.
More information about the trail here