The first work of the people was to raise a great temple to their god--the bloodthirsty Huitzilopochtli--who had led them on. It was begun at once, and around it grew the habitations of the people, the huts made of reeds and mud called _xacali_, such as indeed to-day form the habitations of a large part of Mexican people under the name of _jacales_.[5] This great Teocalli, or "house of god," at the time of the arrival of the Spaniards, was a structure pyramidal in form, built of earth and pebbles and faced with cut stone, square at base, its sides--300 to 400 feet long--facing the cardinal points of the heavens. Flights of steps on the outside, winding round the truncated pyramid, gave access to the summit. Here in the sanctuary was the colossal image of the Aztec war-god--the abominable conception of a barbaric people--and the stone of sacrifice upon which the sacrificial captives were laid. Upon its convex surface the unhappy wretches were successively bound, their breasts cut open with obsidian knives, and the still beating hearts, torn forth by the hand of the priest, were flung smoking before the deity! [Footnote 5: _X_ and _j_ are often interchangeable in Spanish.] Upon the marshy borders of this lake, set in the beautiful and fertile valley of Anahuac, the city rose to elegance and splendour. The _jacales_ gave place to buildings of brick and stone, founded in many cases upon piles, and between them were streets and canals, giving access to the city from the lake. Centre of all was the great Teocalli. The position of the city was peculiar. It was founded upon an island, and was subject to inundations from the salt waters of the lake; for the Valley of Mexico had at that time no outlet for its streams. It formed a hydrographic entity; and in this connection it reminds the traveller of the birthplace of that other strange, prehistoric American civilisation, three thousand miles away to the south-east--Lake Titicaca and the cradle of the Incas. To protect the city from these inundations embankments were made, and other works which attest the engineering capabilities of the people. Four great causeways gave access to the marshy island upon which the capital was situated--structures of stones and mortar, the longest being some four or five miles in length. To-day one of these forms part of a modern street, and the waters of the lake have retired more than two miles from the city. [Illustration: THE VALLEY OF MEXICO: VIEW ON LAKE TEXCOCO; THE MODERN CITY OF MEXICO IN THE DISTANCE.]