38 • The deaTh of azTec TenochTiTLan, The Life of mexico ciTy
Virgin of Guadalupe, and he, Nezahualcoyotl, was the
first to make that causeway.” 36 By giving the ruler credit
for building the Tepeyacac causeway in this historical
representation, the ruler was thereby imbedded in one of
the key lived spaces of the city, a causeway that linked the
island city to the northern shore (figure 2.7). This causeway
served as one of the main arteries of the city through the
sixteenth century and beyond. Archeology has revealed
some of the actual practices that its construction entailed:
it required legions of workers to haul the retaining wooden
pylons and the stone fill to the site. Indeed, many of those
50,000 soldiers—a number that was almost certainly
inflated by the partisan historian—that Nezahualcoyotl
mustered may have begun the campaign by helping build
the causeway that would give them access to the city. 37
Thus, as represented in the city’s histories, particularly
D u rá n’s Historia, two rulers were responsible for the key
works that protected the city from floods and enabled a
freshwater zone to gradually establish itself along the city’s
western flank. Nezahualcoyotl is credited with the north-
ern causeway of Tepeyacac, which ran from the northern
shore to the island of Tenochtitlan; Itzcoatl with the cause-
way of Ixtapalapa, which ran from Tenochtitlan to the
southern edge of the lake. Together these dikes effectively
sealed off the Laguna of Mexico from salty Lake Tetzcoco,
as can be seen in figure 2.7; this effect was noted by colonial
observers who described the “laguna dulce” (sweetwater
laguna) to the west and the saltwater lake to the east. 38
The island itself functioned as the middle part of this
great dike, but it was a necessarily porous link. While
those great works of engineering, the causeways, that were
specifically attributed to rulers were being constructed, a
corresponding system of east–west canals was likely being
dug within the city to allow canoe traffic to pass through
it, as well as allowing the waters flowing into the system
from the west to sieve through the city and flow out into
the eastern Lake Tetzcoco. As the laguna grew less and
less saline, so too the canals into the city that it fed; while
they were never a source of drinking water, the canals and
ditches did sustain urban agriculture.
Despite the engineering feats sponsored by Nezahual-
coyotl and Itzcoatl, this north–south barrier using the
island of Tenochtitlan-Tlatelolco as its middle bulwark
proved insufficient. In 1449, Tenochtitlan was the victim
of terrible floods. The reigning monarch, Moteuczoma
I, turned to his Tetzcocan counterpart, Nezahualcoyotl,
now an old man, to create another dike, this one vastly
more ambitious than the causeway to Tepeyacac. The con-
struction of this dike, which probably occurred during the
dry season of 1449–1450, is recorded by the Franciscan
chronicler Juan de Torquemada, who wrote how rulers of
neighboring cities in the valley contributed to this massive
engineering feat, which he calls the “albarrada vieja” (old
dike): “It was made heroically, with brave hearts attempt-
ing, because it went almost three-quarters of a league [from
the shore] into the lake, which in parts was very deep and
it was four brazas [about sixteen feet] wide and almost
three leagues [about eight miles] long.” 39 The archeologists
Margarita Carballal Staedtler and María Flores Hernán-
dez tried to excavate along this dike but were unable to do
so due to the intensive urbanization of the area. However,
they mined ethnohistorical sources, particularly maps and
aerial photographs, to trace its route. 40 They convincingly
argue that the so-called dike of Nezahualcoyotl ran some
ten miles from the shoreline at Atzacoalco (adjacent to
Tepeyacac) across Lake Tetzcoco, passing along the slopes
of Tepetzinco to the town of Ixtapalapa, closing off the
Laguna of Mexico and increasing the size of the freshwater
enclave around the island city of Tenochtitlan by about
a third. 41 Torquemada confirms its function: “so that the
salty waters didn’t meet the sweet waters upon which was
founded this city of [Tenochtitlan].” 42 The positive effects
of this dike are registered in the annals section of the
Codex Telleriano-Remensis, an indigenous book created
ca. 1553–1563, which notes that 2 Reed (or 1455–1456, some
five years after the dike was finished) was “a fertile year and
thus are painted the green stalks [of maize].” 43
Successful components of the dike system were thereby
created by a succession of Mexica leaders, Itzcoatl, Moteuc-
zoma, and finally Ahuitzotl, each of them also successful
military leaders. The last piece of the causeway-and-dike
system was completed near the end of Ahuitzotl’s reign,
in ca. 1499–1500, and it was in this state that the Span-
ish conquistadores found it in 1519 (figure 2.7, and see fig-
ure 1.10). It was built following a disastrous campaign to
bring more freshwater into the city, described at length in
the next chapter. After the inundation of the city in 1499
(7 Reed), Ahuitzotl sponsored the building of another
short dike, this one linking up the causeways of Tepeyacac
and Ixtapalapa, those already existing north–south barri-
ers, to create a protective border along the eastern shore
of the city, running roughly parallel to the outer dike of
Nezahualcoyotl. 44 The Ahuitzotl dike ran about four
miles and began in the north, at the intersection with the