The walls of Mexico were the foaming surges of her lake. The cities on the shore, when much exposed by defencelessness of site, great wealth of inhabitants, or other causes, to the attacks of enemies, were surrounded by walls, commonly of earth, though sometimes, as in the case of Tezcuco, of stone. These were, ordinarily, of no great height or strength, but sufficient, when well manned, to repel the assaults of the slingers and archers of America. The external fortifications of Tezcuco were, as became the ancient rival of Tenochtitlan, of a more imposing order. The walls were thick and high, with embattled parapets, and deep ditches at the base. The gates were protected in the manner common to the land, by the overlapping, so to speak, of the opposite walls; that is, being made, as they approached each other, to change from their straight, to a circular course, the one traversing upon a greater radius than the other, they thus swept by and _round_ each other, in parallel curves, leaving a long and narrow passage between them, commanded not only by the walls themselves, but by strong stone turrets, built on their extremities. Besides these defences, there was erected within the walls, and directly opposed to each entrance, a small pyramid, elevated fifteen or twenty feet above the walls, and crowned with little sanctuaries,--thus serving a religious as well as a military purpose. In the one sense, these structures might be considered Chapels of Ease to the greater temples of the quarters in which they stood; in the other, they were not unlike the cavaliers, or commanding mounds, of European fortification, from the tops and sides of which the besieger could be annoyed, whilst without the walls, and arrested on his course, when within. Thus, then, there were ready to his hands, fortifications, of which the Spanish commander, now the Captain-General of New Spain, as the unsubdued Mexico was already called, was not slow to reap the full advantage. A strong guard of Castilian soldiers was posted before each gate; a native watchman sat on each turret; and a line of Tlascalan sentries, stepping proudly along in their places of trust, occupied the lofty terrace of the walls. The edifices disclosed to Juan, when he had, with his companions, passed through the staring warders into the town, were similar to those of Mexico,--of stone, and low, though often adorned with turrets. In all cases, the roofs were terraced, and covered with shrubs and flowers; and the passion of the citizens for such delightful embellishments, had converted many a spacious square into gardens, wherein fluttered and warbled birds of a thousand hues and voices. Over these open spaces were seen, in different quarters, the tops of high pyramids and towers, scattered about the town in vast and picturesque profusion.