During the centuries that succeeded this lake had disappeared, low, marshy lands occupying its site. The city, however, was still reached by causeways, eight in number, raised about six feet above the marsh level. In these ended the five main roads leading to the city. A large canal surrounded the capital, and within its circle were smaller ones, all now filled with water, as this was the rainy season. The problem of bridging these under fire was one of the difficulties that confronted the Americans. General Scott decided to approach the city by the causeways of San Cosmé, Belen, and Tacubaya, which were defended by formidable works, the outermost of which was Molino del Rey, a fortified position at the foot of a slope beyond which a grove of cypresses led to the hill of Chapultepec. It consisted of a number of stone buildings, some of which had been used as a foundry, but which were now converted into fortresses. This place was carried by storm in the early morning of September 8, and the stronger position of Casa de Mata, a quarter of a mile from Chapultepec, was captured by a fierce assault the same day. Only Chapultepec now lay between the Americans and the Mexican capital. The stronghold of Chapultepec, of which the places just taken were in the nature of outworks, remained to be captured before the city could be reached from that quarter. Chapultepec is an isolated rocky hill, about one hundred and fifty feet in height, and was surmounted by a large stone building which had been used as the bishop’s palace, but was now converted into a strong fortress. It was well prepared for defence in guns and garrison, and was the most difficult to win of the fortifications of the capital. The western side was the most accessible, but the face of this, above the grove of cypresses which covered its base, presented a steep, rocky, and difficult ascent. To deceive the enemy, a feigned advance upon another section of the city was made on the 12th of September. The two divisions engaged in this returned that night to Tacubaya, near Chapultepec, though a force still threatened the southern causeways. Four batteries had been posted within easy range of the castle of Chapultepec during the night of the 11th, and all next day they kept up a steady fire upon it, driving its defenders back and partly wrecking the walls. On the morning of the 13th the batteries resumed their fire, while the forces chosen for the assault approached the hill from different directions through the fire of the enemy.