The arecibo observatory is the largest radio telescope on earth. The visitor's center has an impressive exhibition about space and the observation of space as well as on the global climate on earth. You can easily spend a couple of hours here and might want to proceed to the close-by Camuy caves.

Arecibo
Arecibo observatory
Cabo rojo
Camuy caves
Carolina
Condado
Culebra
El yunque
Guanica
Gurabo
Isla Verde
Phosphorescent bay
Ponce
Rio Piedras
San juan
Vila Nova De Cacela