Star gazing: set in the lunar landscape of Chile's Atacama Desert, this new residential building for astronomers has to contend with harsh extremes of climate - review of astronomical observatory in Chile

Architectural Review, The, June, 2003 by Catherine Slessor

Extending from the Pacific Ocean to the Andes Mountains, the Atacama Desert in northern Chile is one of the hottest, driest places on earth. Sparsely populated and virtually rainless, the desert plateau is made up of salt basins (salars) and lava flows melded into a desolate, lunar landscape scorched by day, chilled by night and blasted by strong winds. Average relative humidity is around 15 per cent (well below comfort zone levels) and minor earthquakes are common. Humankind's impact on such an inhospitable place is at best precarious, yet for 3000 years, native peoples have resiliently exploited scarce natural resources to colonize the Atacama wilderness, building canals and aqueducts to irrigate fields, using water drawn from underground aquifers. Scattered settlements were established around water sources and, when the Spanish arrived in 1500, the native populace adapted to and absorbed colonial influences. As might be expected, contemporary architecture is scantily represented, but German del Sol's Explo ra Hotel (AR February 1999), a modern tourist estancia that responds to the distinctive culture and spirit of Atacama, is one notable exception. Building in this wilderness is a considerable logistical challenge, but German practice Auer Weber have inventively addressed it in a new building for an isolated colony of astronomers, in which scientific rationale squares up to the rawness of nature.

One favourable consequence of the Atacama's lethal conjunction of extreme climate and harsh topography is perpetually clear skies; the remote terrain is also largely free of the distracting light pollution that accompanies human settlements and activities. Such conditions are ideal for astronomical observation and the European Southern Observatory (ESO), a technical and research federation made up of representatives from ten European countries, currently operates two observatories in the Atacama plateau. Las Sillas was established in 1962, and nearly thirty years later, in 1991, a second base was set up at Cerro Paranal, just inland from the Pacific coast and about 130km south of the town of Antofagasta. Set on top of a 2600m high peak, the Cerro Paranal observatory has an unequalled view of the heavens through the world's most powerful and sophisticated astronomical device, the prosaically named Very Large Telescope (VLT). The Paranal base sustains a sizeable community of astronomers and scientists, who nee d living quarters as well as laboratories, and Munich-based practice Auer Weber (the ESO has its headquarters in Germany) were asked to design a new residential building for the observatory; a sort of hotel for boffins at the end of the world.

So as not to contaminate the night sky with light, the new addition is sited at some distance from the hilltop telescope, but it also had to generally minimize its impact in the landscape. The outcome is a long, low, almost topographic structure partially embedded in the terrain as protection against the scorching sun and scouring winds. The building's two visible elevations are orientated towards the south. east and south-west, away from the main VLT site and the prevailing north winds.

Planning is logical and economical. A long thin bar of 108 cellular bedrooms meets a slightly fatter block of communal spaces at right angles to form an L-shape which encloses a circular central courtyard. Planted with palm trees, succulents and cacti, and equipped with a sybaritic swimming pool, the courtyard is a literal oasis in the desert, as the planting helps to raise and maintain humidity levels within the building. The region's searing daylight is tempered and filtered through a 35m wide geodesic dome clad in panels of translucent polycarbonate sheeting. The gentle geometric undulation of the dome (appropriately resembling a crash-landed flying saucer, but also alluding to the domed telescope housing and the infinite vault of the sky) is the only part of the building to rise above the existing line of the horizon, so the hotel seems barely there. The entrance is also consciously inconspicuous--a long ramp leads down into the ground and sweeps and spirals around the Bondvillain's-lair central courtyar d in a kind of promenade architecturale.

From a distance, the elongated horizontal streak of the main south-west facade seems like an extension of the stark landscape. And in some ways it is, as iron oxide mixed into the concrete renders the building a deep rusty red, matching the hue of the surrounding earth. The layered facade is designed to screen as much sunlight as possible, while still allowing spectacular views of the lunar scenery. Glazing in each bedroom bay is confined to a narrow L-shape, incised into the massive concrete planes, and deep window reveals also help to diffuse glare. At certain points, the inner wall is pulled back from the concrete outer grid to create a terrace running along the edge of the communal dining hall. The prospect of off-duty astronomers lounging on their terrace, savouring the views down to the Pacific, are perhaps more suggestive of an upmarket wilderness resort than a forum for serious scientific endeavour, but the programme emphasized the role of the new building as a place for rest and recreation, and, as w ith all isolated, self-contained working communities (eg oil rigs, monasteries, military bases), participants need some kind of experiential texture to enliven the passing of time.