The various windows in
the structure align with
the risings and the set-
tings of Venus and other
heavenly bodies along the
horizon.

800 ce
, and the major centers in the central regions of Mayan civiliza-
tion collapsed entirely around
900
. A resurgence of Mayan power
developed on the Yucatan peninsula—notably in Chichén Itzá—in the
following period to
1200
, but from the eleventh century the Long
Count fell into disuse, and the record indicates a decline in the rigor of
training for scribes and priests. Thereafter the high civilization of the
Maya passed into history. An array of causes have been put forward
and debated to explain the protracted death of Mayan civilization.
Endemic warfare among confederations of city-states may have played
a role, and the inevitable pressures of population measured against a
fragile system of food production may have produced radical demo-
graphic fluctuations. Compounding such possibilities, two centuries of
drought—the worst in
8
,
000
years—affected the Mayan lowlands in
800–1000
and no doubt took a heavy toll. Researchers have recently
highlighted the problems of deforestation stemming from Mayan tech-
niques of using large amounts of wood to make lime for stucco with
which Mayan monumental architecture was plastered. Deforestation
probably disrupted rainfall patterns and, at least in places, led to soil
erosion and thereby the ruination of agriculture. Mayan civilization
gradually waned, and with it the exquisite system of understanding
nature that the Maya had achieved.
Cactus and Eagle
Central America also saw the rise of Toltec and Aztec civilizations.
Based on irrigation agriculture, between
900
and
1100 ce
the Toltec
city of Tula had
35
,
000–60
,
000
inhabitants, and the Toltecs built what
is technically the largest pyramid in the world, a manmade mountain
of
133
million cubic feet,
1
,
000
feet on a side, and
170
feet high cov-
ering
45
acres at Cholula.
The Aztecs began as a seminomadic tribe, and in the fourteenth and
fifteenth centuries they established the most powerful empire in Cen-
tral America. They built their city of Tenochtitlán in
1325
on a lake
where Mexico City presently stands; according to legend, an omen—
an eagle perched on a cactus—drew them to the lake. The Aztecs
proved to be master hydraulic engineers. The lake, Lake Texcoco, was
saltwater, and Aztec engineers built a huge dike across it to separate a
fresh-water portion (fed by springs) from the brine; they also installed
floodgates to regulate lake levels and aqueducts to bring additional
fresh water to the lake. Each year millions of fish and ducks were taken
from lakes, which also provided a nutritious algae paste. The Aztecs
developed an intensive style of lake-marsh (or lacustrine) agriculture
that involved dikes, dams, drainage canals, and land reclamation, all
produced as public works under state management. Agricultural pro-
duction was literally based on floating paddies known as
chinampas.

