Thank you Shui, Ana and Inma - well chosen - it is indeed part of an important era in Spanish history. I actually wrote a short essay on that period: http://www.dlmcn.com/AlfonsoSexto.html (for a local publication in Almería, drawing from the book "ALFONSO VI - Señor del Cid, Conquistador de Toledo" by Gonzalo Martínez Díez). It seemed worth highlighting the fact that one of Alfonso VI's wives - Zá'ida - is the only Muslim woman in the whole of history who became a Christian queen; (originally, she was the daughter-in-law of the Muslim Ruler of Seville).
When asked what she thought was "el peor momento de la historia de España", the Madrid historian María Lara Martínez replied:
"La batalla de Uclés contra los almorávides en el año 1108 marcó un "antes y un después". Murió Sancho Alfónsez, y Alfonso VI se quedó sin heredero varón. Sancho Alfónsez era un príncipe de dos sangres, pues su madre era la mora Zá'ida. ¿Qué habría pasado si este adolescente hubiera llegado al trono? ¿En qué medida su muerte truncó el proyecto de convivencia de judíos, cristianos y musulmanes?"
The film starring Charlton Heston and Sophía Loren was very well presented; unlike many modern-day productions it at least made an effort to comply with several facts presented in historical documents.
The relationship between the Cid and his King Alfonso VI was not always smooth: for example the Cid did not contribute to the conquest and occupation of the key fortress at Aledo (near Totana in the Region of Murcia, at that time lying deep within Muslim-held territory; my essay contains photos). And the Cid did not participate in the Battle of Uclés.