The People of Gibraltar
1463 - La Capilla de los Duques de Medina Sidonia

Despite its grandiose name, this chapel was just a rather small domed chamber which was once found inside the Tower of Homage of the Moorish Castle complex. (See LINK

The Tower of Homage - Moorish Castle  (1627 - Luis Bravo de Acuña) (See LINK)

The Chapel has its own curious and convoluted history. During the early 15th century Gibraltar had become a base for Moorish pirate raids. Prosperity for the Rock and it Moorish owners while the surrounding Spanish hinterland suffered accordingly. 

In 1436, Enrique Perez de Guzmán, a feudal overlord whose family owned much of the coastline from Tarifa to Cadiz - a favourite area for pirates - decided that enough was enough. He put together his own private army with his son Juan de Guzmán as his lieutenant and attacked Gibraltar. Hes determined to  get rid of its Muslim rulers once and for all. 

But as Robert Burns later reminded us, the best laid plans don’t always work out - particularly when those plans are anything but the best. During an ill-advised attack from the sea Don Enrique was foiled both by his Muslim enemies and by the incoming tide and managing to fall into waters that were deep enough to drown in while dressed in full military armour. History has later dignified this fiasco by calling it the 7th Siege of Gibraltar.

The area of the Bay not far from La Torre del Tuerto and the New Mole (see LINK) where Enrique de Guzmán drowned   (1567 - Anton Wyngaerde ) (See Link)

A horrified Juan de Guzmán immediately withdrew his forces and then  . . . but perhaps what happened next is best described with a quote from Pedro de Medin’s Crónica de los Duques de Medina Sidonia written in 1561:
Don Juan de Guzmán trataba con los moros que le diesen el cuerpo de su padre, y por ningún precio ni ruego no se lo quisieron dar; antes los moros hicieron meter el cuerpo del conde en un ataúd, y lo pusieron colgado de las almenas de una torre que está encima de una puerta que se llama de la Barcina, donde estuvo hasta que este D. Juan de Guzmán su hijo , que fue primer duque de Medinasidonia, fue sobre Gibraltar y la ganó a los moros, y puso los huesos de su padre en una rica caja de madera cubierta con un paño de tela de oro, en una capilla en la Carrahola , que es la torre del homenaje y la principal del castillo de Gibraltar, donde están hoy. 
Perhaps it is worth mentioning that “la carrahola” must be a misspelling for “la calahorra” - the medieval name for the Tower of Homage described by Pedro de Medin. Also worth a few lines is the fact that Pedro de Medin had actually seen “los Huesos” with his own eyes. Although they were jumbled up together he though there were enough of them to comprise a complete skeleton. They were, he wrote, very white, very clean and odourless.

The Calahorra of the Moorish Castle complex    (From a 19th century engraving)

1462 is mostly remembered as the date in which Spanish forces during the 7th siege finally captured Gibraltar from the Moors - and managed to keep hold of it until 1704 when it was once again lost - this time to Anglo-Dutch forces.  As far as I can make out none of the mainline histories of Gibraltar make even a passing reference to the Chapel - and yet the recovery of his father’s body must have been one of the most important factors driving Juan de Guzmán during the 7th siege.

This was an age in which “honour” was everything and having your father’s body on permanent display in what was according to other sources not in an “ataud” or coffin but in a wicker basket - or “barcina” - for such a long period of time that it became the name to what is now called the Casemates.

Given all this I would say that the chapel was set up by Don Juan not very much later than 1462 making it one of the oldest Christian places of worship on the Rock and for many years later something of a tourist attraction. 

La Capilla - The text reads in English “The sepulchre where one can find the bones of the Count covered in brocade”     (1567 - Anton Wyngaerde)

As suggested by Medin - the Alcaldes of the Rock for whatever reason seemed loath to allow the bones to be removed from the Chapel.
Y aunque aquella cibdad fue de los señores desta casa de Niebla , no quisieran mudar los huesos del conde, ni traerlos a su enterramiento de Sevilla, sino dejarlos allí por memoria de su muerte. 
Y después que la cibdad de Gibraltar ha estado y esta por los reyes de Castilla, tiénense en tanta veneración aquellos huesos del conde de Niebla, que la segunda cosa porque se toma homenaje a los alcaides; de Gibraltar, es que los huesos del conde de Niebla que allí le entregan, no los consentirá sacar de allí; porque quieren los reyes honrar la cibdad con que estén en ella los huesos de un tan excelente señor. 
The Flemish cartographer Anton Wyngaerde seems to have been obsessed with the drowning of poor Don Enrique mentioning his “bones” several times in his well know 1567 drawings. 

The Moorish Castle - the caption reads in English as  “In this tower are found the bones of the noble count in Gibraltar”  (1567 - Anton Wyngaerde  - detail)

Then in 1612 - exactly one hundred years after Pedro de Medin’s visit, the bones were removed from the Capilla by the Guzmán family and taken to la Iglesia de Nuestra Señora de la Caridad in Sanlúcar de Barrameda - a town which had been the private property of the family since 1297. 

Shortly after their removal Alonso Hernández del Portillo (see LINK) in his 1627 Historia de Gibraltar somewhat surprisingly casts doubts on whether the bones were in fact those of Enrique Perez de Guzmán:
En un aposento de estos (in the Moorish Castle) están los huesos del conde de Niebla Don Enrique de Guzmán, que murió sobre esta ciudad . . . . adonde de ordinario se dice misa por su anima, de que han tenido y tienen buen cuidado los Duques de Medina sus sucesores. 
Otros creen que estos huesos son de Don Juan de Guzmán primero Duque de Medina, a quien los Moros la entregaron
Whether Alonso was right or not from 1612 onwards the Chapel no longer had any purpose and as far as I can make out ceased to exist as a place of worship.