required a 
the land 
an would 
loors and 
different 
it. These 
iphic relief 
Terences in 
that was 
abor and 
11 sinking 
le sinking 
compacted 
rface is a 
ort out the 
basin, the 
platforms 
eremonial 
aundations 
the latter 
inferences 
ight record 
ng for the 
Registers 
?0) enable 
. Average 
zones in 
as mounds 
Filomene 
Nacional 
through 
danger 
¡chnical 
iout the 
hat, at a 
that the 
formed 
irth and 
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. 
As r—.- I ¡ — 
I il "*■ * 
/ JW i i i i 
i. 
I 
,1 
V, 
\\ 
K'bt***i 
r* H"«*-•*»»*•** 
_.JSF 
f Ui ; -+¿ N.. t At. m 
■ i t 
<. 1 
is- 
( / \ i. 
I Ml 
- W / 
X 
I Sf ¿fe !*”■ Vi 
« i hiimii j 
w ' i x ^- 
iV / 
ï* «HrfWhi M oft*. ’jh) 
7 _ §& if i*-. 
■ it 
i * w — V- . i - ** 
‘1 y f 
if >•»-** mix**** 
.h! ~i**~-*> | v 
i / ¿A- 
hr*—s $ $ 
! ** j 
^ ■« 
——mil v .J 
Jl > • ■*»* i i 
4k 
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 
403