On the twenty-seventh, therefore, Soult was able to press close in to Oporto, for the line of the Avé is but fifteen miles north of the city. On approaching the heights which overhang the Douro the French found them covered with entrenchments and batteries ranged on a long front of six or seven miles, from San João de Foz on the sea-shore to the chapel of Bom Fin overlooking the river above the town. Ever since the departure of the French from Orense and their crossing of the frontier had become known, the whole of the populace had been at work on the fortifications, under the direction of Portuguese and British engineer officers. In three weeks an enormous amount of work had been done. The rounded summits of the line of hills, which rise immediately north of the city, and only half a mile in advance of its outermost houses, had been crowned with twelve redoubts armed with artillery of position. The depressions between the redoubts had been closed by palisades and abattis. Further west, below the city, where the line of hills is less marked, the front was continued by a deep ditch, fortified buildings, and four strong redoubts placed in the more exposed positions. It ended at the walls of San João da Foz, the old citadel which commands the mouth of the Douro, and had in this direction an outwork in another ancient fort, the castle of Quejo, on the sea-shore a mile north of the estuary. There were no less than 197 guns of various calibres distributed along the front of the lines. Nor was this all: the main streets of the place had been barricaded to serve as a second line of defence, and even south of the river a battery had been constructed on the height crowned by the Serra Convent, which overlooks the bridge and the whole city.