The city of Barcelona, one of the most populous and important in Spain, is not naturally a place of great strength.

It is situated on a plain close to the sea, and its defenses, although extensive, were not very formidable against a strong army provided with a siege train.

To hold them fully required a much larger force than was disposable for the defense.

The garrison was, however, fully equal in strength to the force of Peterborough, and should have been able to defend the city against an army vastly exceeding their own numbers.

Ten bastions and some old towers protected the town toward the north and east; between the city and the sea was a long rampart with an unfinished ditch and covered way; while to the west, standing on a lofty elevation, the castle of Montjuich overlooked and guarded the walls of the city.
From the center of the sea face a mole projected into the water, guarding a small harbor.