Arecibo Observatory, ☎ 878-2612, . Hours: W. - Fr. Noon - 4PM. Sat., Sun. and most holidays 9 AM - 4PM. Located approximately ten miles south of Arecibo on a fairly deserted roadmountainous and somewhat isolated road the Arecibo Observatory is home to the world's largest radio telescope operated by Cornell University. The visitor's center is decent with working bilingual exhibits. There are no tours of the telescope, itself, however you can view the telescope from a platform. Bring an umbrella, in case of rain. Also be sure to have comfortable walking shoes for the 500 steps up the mountain.Adults $5. Children and Seniors $3.