According to people who were on the set during the production of El Cid (as interviewed for the extras section of the DVD) Charlton Heston and Sophia Loren hated each other while making this movie. Part of the reason could be that Loren was paid more than Heston ($1 million, the first time a woman had been paid that sum for acting in a single motion picture). As can be seen in the finished film, during many of the "love" scenes, Heston refused to look at Loren for more than a glance. The director tried take after take, imploring Heston to look into the eyes of the woman he loved, but Heston couldn't bring himself to do it. Regarding his deathbed scene, he later claimed that he was "looking into the future," rather than into the eyes of his wife.
According to the legend of El Cid, in his youth Rodrigo came across a leper sinking in quicksand crying for help, but none of the bystanders dared touch him. Rodrigo pulled him from the bog, clothed him in his cloak, housed him in a barn and went to get him some food. When he returned, he found the leper had transformed into an angelic figure that identified himself as St. Lazarus. He said "For your bravery and kindness you will enjoy success as a warrior. You will win battles upon battles and never know defeat". In a nice nod to the legend, the film contains a scene wherein the banished Rodrigo encounters a thirsty leper who begs a drink. After unhesitatingly offering his own pouch, the Leper thanks him by name. "Who are you?" asks Rodrigo. "I am called Lazarus." The leper answers. Then he crosses Rodrigo with his staff. "May helping hands be extended to you everywhere you go, my Cid."
After the death of El Cid, Babieca was never mounted again and died two years later at the incredible age of forty. His master had asked that his wife and famous steed be buried with him at the Monastery of San Pedro de Cardeña. But unfortunately their remains were removed after the Peninsular Wars and taken to the cathedral in Burgos where they were finally interred and where they currently rest today.
Another theory for the horse name of Babieca is that this horse came from the Babia region. This was the reason that the horse became a great war horse.
By the time this was released, Allied Artists (formerly Monogram) had ceased production and was only distributing independent productions. The rights for the Western Hemisphere were acquired from Samuel Bronston. This gave Allied Artists its only full-blown epic, which was given a roadshow presentation followed by a general release.
El Cid did not die as depicted in the film. He died peacefully in 1099 while ruling his principality on the coast of Spain. His wife Jimena continued to rule after his death.
El Cid's sword "Tizona" can still be seen in the Army Museum (Museo Del Ejército) in Madrid. Soon after his death, it became one of the most precious possessions of the Castilian royal family. And in 1999, a small sample of the blade underwent metallurgical analysis which partially confirmed that it was made in Moorish Cordoba in the eleventh century, although the report does not specify whether the larger-scale composition of the blade identifies it as Damascus steel. In 2006 "El Museo Del Ejércitp" (The Army Museum) was moving from Madrid to Toledo and apparently the sword was not available to be seen in public. El Cid also had a sword called Colada.
It wasn't until viewing the finished film at the premiere that Dr. Miklós Rózsa discovered that roughly 20% of his score had been eliminated. He didn't do another score for producer Samuel Bronston.
One well-known legend about the Cid describes how he acquired his famous war-horse, the white stallion Babieca (Bavieca). According to this story, Rodrigo's godfather, Pedro El Grande, was a monk at a Carthusian monastery. Pedro's coming-of-age gift to El Cid was his pick of a horse from an Andalusian herd. El Cid picked a horse that his godfather thought was a weak, poor choice, causing the monk to exclaim "Babieca!" (stupid!) Hence, it became the name of El Cid's horse.
Perhaps somewhat surprisingly, Charlton Heston himself was not overly impressed by the finished film, suggesting in his 1995 autobiography "In the Arena" that the film might have been better if William Wyler had directed it instead of Anthony Mann.