The Contreras railway viaduct is located between the provinces of Valencia "Valencia (province)") and Cuenca "Cuenca (province, Spain)") and crosses the homonymous Contreras reservoir within the Cabriel Valley Biosphere Reserve. It is part of the high-speed section of the Community of Madrid-Castilla-La Mancha-Valencian Community. Until 2016, it held the record for the bridge with the longest concrete arch span in Spain and stands out for its slenderness and visual beauty. Now, the largest is the Alcántara reservoir viaduct, built in 2019 for the Madrid-Extremadura High Speed ​​line.

It was designed by the civil engineer Javier Manterola Armisén[1]​ and the construction management was by the civil engineer Pablo Jiménez Guijarro, assigned to ADIF.

This arch-built bridge resists great stress due to its great length and slenderness. To build it it was necessary to use high-strength concrete whose compressive strength after 28 days is 70 MPa. In addition, the deck has a concrete box section and has a width of just over 14 meters. It is made up of 14 spans of variable length. The end openings have a length of 36.2 meters while the central ones measure 43.5 meters.

The main difficulty in the construction process responds to environmental requirements given that it had submitted its application as a Cabriel Valley Biosphere Reserve for UNESCO. The first sections have been made using a self-launching formwork system with fixed formwork and filling them with concrete. These sections correspond to the bases of each semi-arch. The rest of the semi-arches are built by advancing a formwork carriage and are provisionally supported by steel braces that are supported by an additional steel structure.

The central arch has been the most difficult part of the project, as it could not be built and placed due to its great magnitude, its construction has progressed parallel to that of the deck so that the construction of the deck favored the advancement of the arch. Finally, it remained to join the two halves of the bridge. After placing the last part that closed the arch, it was possible to place the last part of the deck on it, thus completing its construction.