One of the most important structural changes and one of the first building works carried out in the Alhambra after the Christian conquest was the construction of a large water deposit in the river bed between the Alcazaba and the rest of the Alhambra. D. Íñigo López de Mendoza, 2nd Count Tendilla and 1st Marquess of Mondéjar, (Guadalajara?, 1440-Granada, 1515), also known as the "Great Tendilla", was the Governor of the Alhambra at the time and commissioned the building of this enormous water deposit. The most spectacular feature of this building, which survives today, is its splendid vaulted ceiling.
The water deposit was built in the dry river bed between the Alcazaba and the inner medina of the Alhambra, in order to guarantee the water supply not only for the Palace itself but also for the city of Granada. The water deposit is rectangular in shape with two naves linked by six doors with semicircular arches. The two naves are covered by barrel vaults in which wellheads were installed to enable the water to be extracted. The roof of the water deposit is now covered by the area known as the Plaza de los Aljibes (Square of the Water-Deposits). From the outside only the entrance is visible, as this area has undergone so many changes since the 16th century that its original appearance has been lost.
The 2nd Count of Tendilla was appointed Governor of the Alhambra and Captain General of Granada by King Ferdinand and Queen Isabella. (Source: Official Guide to the Alhambra)