The bridge started being built in 1751 and took a total of 42 years to build and claimed the lives of 50 builders. There is a chamber beneath the central arch that was used for a variety of purposes, including as a prison. During the civil war (1936 to 1939), both sides allegedly used the prison as a torture chamber for captured opponents, killing some by throwing them from the windows to the rocks below at the bottom of the El Tajo gorge. One enters the chamber via a square building that was once the guard-house. It contains an exhibition describing the bridge's history and construction.