It was, in fact, by far the strongest point in the position of the besieged.
Standing on a commanding height, it was abundantly capable of defense even against a regular siege, and its reduction was always regarded as a most formidable enterprise, to be undertaken at leisure after the capture of the town.

Its only weakness lay in the fact that surrounding it on every side were numerous ravines and hollows, which would afford concealment to an assailant, and that trusting to the extraordinary strength of their position the garrison of Montjuich might neglect proper precautions.
One morning before daybreak the earl, accompanied only by Jack and a native guide, left the camp on foot, having laid aside their uniforms and put on the attire of peasants, so that the glitter of their accouterments might not attract the attention of the enemy's outposts.
Making a long detour they approached the castle, and ascending one of the ravines gained a point where, themselves unseen, they could mark all particulars of the fortifications.

Having carried out his purpose the earl returned to camp with his companion without his absence having been observed.

The observations which Peterborough had made confirmed the reports of the peasants, that the garrison kept but a negligent watch, and he at once resolved upon making the attempt; but to none of his most intimate friends did he give the slightest hint of his intentions.
To disguise his views he called councils of war both in the camp and fleet, wherein it was resolved, with his full consent, that the siege of Barcelona should be abandoned, and that the army should be immediately re-embarked and conveyed to Italy.

Accordingly the heavy artillery was conveyed on board ship, the warlike stores collected, and the troops warned to be ready for embarkation.