Arecibo is a mountain town in Puerto Rico. There is a large meteorite crater nearby in which US astronomers have built the world's largest radio telescope, the Arecibo Ionospheric Observatory.
FBI Special Agents Dana Scully and Fox Mulder journeyed to Arecibo in late 1994 to investigate reports that the defunct Ionospheric Observatory was secretly receiving transmissions from an extraterrestrial source. — (Little Green Men)