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The participation of the Prospection Laboratory in archaeological
projects undertaken in lake areas such as: Terremote-Tlaltenco
(Serra 1986); the archaeological rescue of the Xochimilco zone
(Lazcano 1995); Loma Alta and Guadalupe, Michoacân (Hesse
et. al, 1996) and more recently in Santa Cruz Atizapân, Mexico
State, have enabled the localization and study of these ancient
islets. The results of these projects contributed in determining
the presence of residential units, or larger structures of
communitarian or ceremonial character.
Thus Avila’s work (1991) in the Iztapalapa and Tlahuac zones
recorded the existence of chinampas and islets built by their
dwellers. These represent artificial mounds raised upon the
average level of the lake’s surface, wherein the buildings were
put up, and where the inhabitants undertook all of their main
activities (Rojas 1995). Data collected during the studies at
Tlaltenco and Xochimilco show that these islets could only
measure 50 cm or exceed 1.50 meters in height, while its shape
might be round, oval, or elongated in the shape of a 20 to 50 m
long at its central axis. These features are closely related to the
form and the height of some of the mounds now seen on the
city’s streets. As Masari et al. (1989) has documented thoroughly,
islets built based on the accretion of land use to constantly sink,
thus making adding soil periodically necessary to keep the surface
above the water level. This causes a progressive compaction of
soil which has gone normally unnoticed. Namely, these
differences in soil pre-compaction weren’t discovered till 1940
when the water extraction rate increased thus causing the rapid
sinking of the city and the appearance of those mounds in certain
areas of the city.
4.1 Recording of Mounds
Based upon a documental study, cartographic observations were
verified, knolls on the city streets were recorded so to produce
maps that could emphasize them, for they might constitute
ancient islets. As has been stated before, some previous
measurements (Marsal & Masari 1969; and Kumate & Masari
1990) were used, since they show the progressive sinking of the
city.
The investigation gave priority to nahuatl toponyms which
directed the search towards neighborhoods with an irregular and
narrow urban plan, a feature of ancient settlements. At these zones
every street was analyzed thoroughly, recording every knoll on
a map. At the same time a photographic record was undertaken.
Thus zones such as Zacahuizco, Tetepilco, Tultengo, Iztapalapa,
Culhuacan, Iztacalco, Churubusco, Coyoacân, Acoxpa, and
Coapa were studied.
By the end of this stage, we had a clear idea of the areas wherein
mounds were concentrated, representing the larger archaeological
structures lying beneath the pavement of southern Mexico City,
especially downtown area. At the present, we have a database
pinpointing these sites, their structures and some of their features.
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Figure 2. Areas of Mexico City where mounds are
concentrated (dotted lines)
5. RESULTS
The map based on González Aparicio’s study (1973) gathers the
documentary and archaeological information available in the
seventies. It determines the probable places of pre-Hispanic
settlement in the lakeshores and in the lake itself. One of the
main features of this map is that it refers both to Tenochtitlán’s
main islet and to the smaller settlements as well. For the first
time it offered a clear idea on the distribution of the pre-Hispanic
settlements, which by recent data, coincide in many cases with
the mounds found in some of the city’s traditional neighborhoods.
For instance, the Aztlacalco area, which shows a great
concentration of topographic knolls, is spread across most of
the Roma neighborhood. Zacahuizco and Tetepilco, in turn, show
concentration zones with clearly drawn mounds and they preserve
their former pre-Hispanic names. At the Tultengo and Mixhuca
zones we haven’t found any association with street mounds thus
far. However, downtown Mexico City, including the erstwhile
Tenochtitlan islet, corresponds to the distribution of a great
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