The Puerto Ricans reverently refer to it as 'El Radar.' To everyone else it is simply the largest radio telescope in the world. Resembling an extraterrestrial spaceship grounded in the middle of karst country, the Arecibo Observatory looks like something out of a James Bond movie - probably because it is (007 aficionados will recognize the saucer-shaped dish and craning antennae from the 1995 film Goldeneye).

The 20-acre dish, set in a sinkhole among clusters of haystack-shaped mogotes, is planet Earth's ear into outer space. The telescope, which is supported by 50-story cables weighing more than 600 tons, is involved in the SETI (Search for Extraterrestrial Intelligence) program and used by on-site scientists to prove the existence of pulsars and quasars, the so-called 'music of the stars.' Past work has included the observation of the planet Mercury, the first asteroid image and the discovery of the first extra-solar planets.

Top scientists from around the world perform ongoing research at Arecibo, but an informative visitors center with interpretative displays and an explanatory film provide the public with a fascinating glimpse of how the facility works. There's also a well-positioned viewing platform offering you the archetypal 007 vista.

To get to the observatory follow Hwys 635 and 625 off Hwy 129. It's only 9 miles south of the town of Arecibo as the crow flies, but the rollercoaster ride through karst country will make it seem more like 90.