Rock engravings can be found all around La Silla, most of them on the eastern slope of the mountain, towards the locality called "El cementerio Indio", in particular, on both sides of the "Quebrada Los Tambos" (whose head is directly below the 3.6-m telescope). In February 1990, D. Ballereau (Observatoire de Paris, DASGAL, Meudon, France) and H. Niemeyer (Sociedad Chilena de Arqueología, Santiago, Chile) carried out a complete photographic and topographic survey of the engravings of this quebrada and then compiled a photographic atlas of over 1000 black-and-white pictures and hundred of color slides. Several sets of contact prints were made, one of which was deposited at the library in La Silla. The article published in the Messenger contains information on the geography and the history of the area, to help to situate the rock art and prehistoric sites of La Silla in relation to the ancient history of the "Norte Chico". Below is a summary of this article.

Geographical and Historical Context

In the area where the observatory has been set up, four major physical features can be distinguished from east to west: the high cordillera, the mid-altitude mountain range, the wide valleys which cross them, and the coastal plain. This mountain is situated in the basin of the "Río Los Choros", which does not originate in the high cordillera, which explains why there is no permanent watercourse in the bed of this "Río". However it may be presumed that in the first millennium of our era, rainfall was more abundant that it is now, hypothesis that is supported by the presence of prehistoric sites around La Silla. The archaeological sites of La Silla have not been excavated, but based on similarities between the rock art styles, it is generally accepted that the signs of occupation at La Silla can be attributed to "El Molle" complex (the first culture in the north of Chile).

The Rock Art Sites of La Silla

Ballereau and H. Niemeyer began their exploration of the east slope of Cerro La Silla at the dormitories near the Hotel. Further down (at an altitude of 2.000 m), they found a set of engravings on a vertical panel in three parts, facing south east (Fig. 1). This triptych was carved by a single artist and over a short period of time, because the patina is uniform; there are two scenes showing men and animals together and strange geometrical figures, whose meaning could not be guessed. The richest site in engravings, however, is located beyond the Quebrada Los Tambos, area that can be observed from the outside catwalk of the 3.6-m telescope. The rock engravings are only one hundred meters below this road (Fig. 2).

Figure 1	Figure 2

A few hundred meters down the higher part of this Quebrada, a series of various stone tools can be found (Fig. 3). The majority of the engravings in this quebrada are seen on the thousands of granite blocks scattered over the western slope. Continuing with the route, the explorers went towards Cerro Las Vizcachas, they passed the SEST and one kilometer further they could observe some dark blocks of stone. Here, they discovered one of the most beautiful groups of engravings of La Silla, (Fig. 4) The delicate central spiral symbolizes a serpent while the rest of the space is taken up by strange little figures, together with some simple geometric motifs and quadrupeds.

Figure 3	Figure 4

The La Silla Rock Art Style

The great variety, size, and the diversity of themes of which the engravings are composed often make them authentic works of art. At La Silla, the passing of centuries can be felt at the site. Some rocks have been fissured by weathering, in others, the surface has flaked due to thermal or chemical action and the drawings have been lost forever. The engravings of La Silla can be divided into two well-defined groups: abstract and figurative designs.

Abstract Designs

A large quantity of geometrical signs are found, endlessly repeated: plain circles or circles with rays (internal or external), isolated, concentric or in series, plain rectangles or rectangles with internal parallel undulating motifs, Greek patterns, maze-like designs. See, for example Figure 5, where the central element is a closed undulation often seen at La Silla, while Figure 6 shows numerous surface elements, isolated from one another and with internal parallel lines. A fine example of the graphic expression that could be termed "integral structure" can be seen in Figure 7 (situated very near the road to Las Vizcachas, at level with the SEST), where it is difficult to determine any guiding principle in this jumble of circles, curves or segments.

Figure 5	Figure 6	Figure 7

Figurative Drawings

These drawings mainly depict human outlines and animals. The anthropomorphous generally have a simple structure, a few lines representing the limbs and a dot for the head, but sometimes the style is more elaborate. The body is marked by thick lines, feet and hands are portrayed with toes and fingers, the head has a a mask and bears a large ceremonial headdress. This type of figure is shown in Figure 8. Figure 9, on the other hand, shows a highly stylized human form, identifiable by its two small eyes and the two hands with five fingers. Animal shapes are very numerous and camelidae can be identified by their long necks. The scene in Figure 10 has the most plentiful animals of the entire site, nearly 25 animals and some human figures.

Figure 8	Figure 9	Figure 10

In Figure 11, two figures can be seen whose morphology is distinguished by a "thick" body, i.e. a certain area of the rock has been hollowed out by repeated impacts. They have neither hands nor feet. The style is unique at La Silla and they bring to mind representations of the shamans, common throughout pre-Colombian America.

Figure 11