For here the ground descended gradually, while to the east it shelved very steeply down to the town, and an external defence was unnecessary and indeed impossible. The outer line all round (i.e. the third line on the west, the second line on the rest of the circumference) had as its base the old walls of the external enclosure of the mediaeval Castle, modernized by shot-proof parapets and with tambours and palisades added at the angles to give flank fire. It had a ditch 30 feet wide, and a counterscarp in masonry, while the inner enceintes were only strong earthworks, like good field entrenchments; they were, however, both furnished with palisades in front and were also ‘fraised’ above. The Donjon, which had been strengthened and built up, contained the powder magazine in its lower story. On its platform, which was most solid, was established a battery for eight heavy guns (_Batterie Napoléon_), which from its lofty position commanded all the surrounding ground, including the top of the hill of San Miguel. The magazine of provisions, which was copiously supplied, was in the church of Santa Maria la Blanca. Food never failed--but water was a more serious problem; there was only one well, and the garrison had to be put on an allowance for drinking from the commencement of the siege. The hornwork of San Miguel, which covered the important plateau to the north, had never been properly finished. It was very large; its front was composed of earthwork 25 feet high, covered by a counterscarp of 10 feet deep. Here the work was formidable, the scarp being steep and slippery; but the flanks were not so strong, and the rear or gorge was only closed by a row of palisades, erected within the last two days. The only outer defences consisted of three light _flèches_, or redans, lying some 60 yards out in front of the hornwork, at projecting points of the plateau, which commanded the lower slopes. The artillery in San Miguel consisted of seven field-pieces, 4- and 6-pounders: there were no heavy guns in it.