After the British took Gibraltar in 1704 they further strengthened these fortifications, flooding the land in front and turning the curtain wall into the Grand Battery.

Gibraltar is accessible by land only along a narrow isthmus overlooked by the Rock, which is too steep to be climbed on its east and north sides.

The northern approaches to the town were defended by a castle on the slopes of the rock, from which walls built in the Middle Ages ran down to the shore of the Bay of Gibraltar.

Portillo describes the Giralda tower as "a redoubt of very great strength and capable of containing sufficient numbers to defend the place, as was seen in the year 1333 when besieged by King Alfonso.

Vessels landing at the wharves by the old mole could gain entry through these fortified gates just south of the North Bastion.

The Italian Engineer Giovan Giacomo Paleari Fratino was commissioned by Philip II of Spain to improve the defenses of Gibraltar in the 1560s.

[1] The foot of the glacis in front of the north bastion, and part of the curtain wall leading towards the Rock, was washed by the water of the bay.

[1] Between 1731 and 1734 the area in front of the land wall, which had been a marsh, was excavated to a depth of 2 feet (0.61 m) lower than lower-water level in the bay.

[12] Governor Henry Nugent was mortally wounded on 9 November 1704 at San Pablo Battery (North Bastion).

[20] At the start of the Great Siege of Gibraltar (June 1779 – 7 February 1783), engineers built a "cavalier" (elevated firing platform) for five guns within the north bastion, by then considered a part of the Grand Battery.

The Giralda Tower site, across the road from the Grand Battery, would link tours of the northern and western defences.