waTeR and The sacRed ciTy • 35combine into one enormous lake. However, they were care-
fully manipulated over centuries to turn the high-altitude
valley into a hospitable environment for agriculture (fig-
ure 2.7). 27 The southern lakes, named for the main cities
on them, Chalco and Xochimilco, were certainly the most
important, as they were freshwater lakes fed by springs
and rivers, allowing for agriculture around their shores;
the largest of the other three lakes, Tetzcoco, was saline,
providing an abundance of edible flora and fauna, such as
fish and those algae patties, “small cakes made from a sort
of ooze which they get out of the great lake,” that the Span-
ish conquistador Bernal Díaz del Castillo praised as tasting
like cheese—as well as salt. 28 By the thirteenth century,
the Nahuatl-speaking residents of the southern lakes had
a fully functioning system of intensive agriculture, building
rows of raised beds out of the nutrient-rich muck of the
lake bed, which would be dredged out and piled into rect-
angular plots, the sides secured with deeply rooted trees. 29
These chinampas were, and still are, marvels of ecological
engineering and intensive agriculture. The dredged areas
around them created a system of canals, providing both
constant irrigation and transport to markets in the cities
around the lake. Intensely productive, the chinampas that
the southern peoples created provided the basic foodstuffs
of the Mesoamerican diet: squashes and chilies, greens and
fragrant herbs, and of course, maize; even today, the chinam-
pas of the Chalco region produce flowers and vegetables for
the Mexico City market. By the fifteenth century, these
verdant gardens of Chalco and Xochimilco were supplying
the markets of Tenochtitlan with their abundant goods.
The freshwater of these southern lakes was protected by
two phenomena: the southern lakes are at slightly higher
altitudes than the rest of the system, meaning the fresh-
water from these lakes would drain downward into the
saltwater Lake Tetzcoco. In addition, a natural bottleneck
created by the rising flanks of the hill of Huixachtlan (later
known as Cerro de la Estrella) on the east and the Pedre-
gal, a rocky lava flow to the west of the town of Co yoacan,
further protected the inlet to these lakes. Normally, excess
freshwater flowed through this bottleneck into Lake
Tetzcoco. But during the rainy season, the swelling salty
lakes in the north threatened the chinampas; if a large vol-
ume of water poured into the system from the north, it
would reverse its normal flow, surging back through the
bottleneck to flood Lakes Xochimilco and Chalco with salt
water. By the 1420s, residents of the southern lakes had pro-
tected their precious freshwater zone by building a raised
causeway that served, as would all the causeways in the
system, as a dike; it spanned a natural bottleneck, running
nearly two miles from the base of the hill of Huixachtitlan,
at the town of Mexicaltzinco, across to Huitzilo pochco,
which lay adjacent to the Pedregal. 30 This causeway/dike
of Mexicaltzinco may have had removable barriers in it to
allow the southern lakes to follow their normal drainage
patterns into Lake Tetzcoco, as well as for canoes to pass
through; during flooding season, these openings would
have been closed to protect the chinampa zone.
So, capturing a moment in 1325, the page of the Codex
Mendoza registers both cosmic templates and the lived
spaces of the valley. Well to the south of Tenochtitlan,
those industrious residents of Chalco and Xochimilco
were constructing the most ambitious program of land
reclamation and water control ever seen in the valley (see
figures 1.1 and 1.3). 31 The construction of thousands of
hectares of raised-bed chinampas and the harnessing of the
agricultural potential of the lakebed allowed for a popula-
tion explosion in the subsequent centuries. 32 From their
rocky island in salty Lake Tetzcoco, the Mexica of Tenoch-
titlan were well aware of this, making the conquest of the
Chalco region the centerpiece of the military campaigns
of the emperor Moteuczoma I (r. 1440–1468). By the six-
teenth century, when the Codex Mendoza was painted, the
nascent Mexica city at the moment of origin, a year identi-
fied as being 1325, was remembered as a large chinampa, the
fertile plot made by human hands that made the survival of
the altepetl possible; the Codex Mendoza page shows that
the familiar chinampa and its carefully controlled canalized
waters, life-giving, abundant, were the microcosm of the
city itself.
But even before, in the early fifteenth century, the resi-
dents of Tenochtitlan witnessing the “Chalco miracle” to
the south understood that they could harness equiva-
lent ecological phenomena to create a similar freshwater
zone in their western corner of Lake Tetzcoco, which is
called the Laguna of Mexico (figure 2.7); modern scholars
in the wake of Wittfogel, including Ángel Palerm, Luis
González Aparicio, Teresa Rojas Rabiela, and Perla Valle,
have reconstructed the workings of this system. 33 Like the
southern lakes, this western part of the valley holding the
laguna sits at a slightly higher elevation than the east, and
this phenomenon would be quite visible during the dry
season, when the laguna would dry up to swampy condi-
tions. The laguna is also fed by numerous rivers and springs
flowing in from the west, meaning that its water is sweeter