This hill was the subject of archaeological surveys by General Centeno in the years 1925 and 1926 trying to find Napoleonic military files from when the French in their retreat blew up the fortress.

Oliver Copons believes that the great fortress was already built back in 865 when Muslims invaded the Castilian plateau led by Al-Mundhir of Córdoba.

Twenty years later the Asturian monarch Alfonso III ordered Count Diego Rodríguez Porcelos to repopulate and re-fortify Burgos, having triumphed in the Battle of Briviesca and in defending Pancorbo.

Probably during the reign of Alfonso VIII of Castile the first great transformation occurred, as experts builders altered the castle to fit the Mudéjar taste of the time.

Castilian king Henry IV made the second change, mainly for beautification, turning the castle into a palace with halls, chambers and chapel.

Due to difficulties with supply and French reinforcements moving up from Andalusia he was forced to raise the siege after a number of failed attacks, retreating to the Portuguese frontier.

Is in this year king Alfonso prisonered to Don Frederick, his brother, in Burgos, and sending him get into the castle and put in a chest that was filled with sharp irons and died there."

During the Early Modern Age and because of the evolution of military techniques, and the fact that Spain's wars were fought overseas, the castle gradually lost its defensive function.

During the War of Independence the city regained its strategic position and the French proceeded to strengthen the castle's defences as a strong point which could dominate the Castilian plain.

The Castle of Burgos played a key role in the communication system with the semaphore line devised in Spain in the 19th century.

The remains of the fortress, in a state of ruins, has allowed its qualification as a museum and interpretation center, opened in 2003 and visitors can also see the well and the tunnels, known as Cueva del Moro.

"For that this Castle was safer and it not could take by thirst, made its founder near its entrance, on the inside, a so deep well, which for down to the birth of water has around a snail-shaped stone staircase and three hundred thirty-five steps with its skylights in places that give light, although low, and is so artfully done that looks like work of enchantment.