Tour description provided by Viator

A trip to Puerto Rico is not complete without descending into the depths of a million year old cave! Few cave systems in the world are as massive or dramatic as the Rio Camuy Cave Park. If that's not enough, wait until you see the Arecibo Observatory, the world's largest radar/radio telescope, nestled in the tropical mountains of northern Puerto Rico.

This tour takes you from San Juan to Northwestern Puerto Rico, part of the third largest underground river cavern system in the world. You'll enjoy a safe, guided tour of the marvels. From sinkholes and cathedral-like caverns to views of the mysterious river and its eons-old stalactites and stalagmites. Be sure to wear comfortable, non-slippery shoes! This tour also takes you to where you'll see the largest radar/radio telescope. Operated by Cornell University, the telescope probes the ionosphere, examines planets and monitors natural radio emissions from distant galaxies, pulsars and quasars.

The caves at Camuy are actually 45 million years old, but it took a few million years for nature to adorn their towering ceilings with crystalline stalactites, their walls with flowing stone tapestries and their floors with mushroom mounds of stalactites. Few cave systems in the world are as massive or dramatic as the Rio Camuy Cave Park; none have a thundering tropical river traversing countless miles of uncharted channels. Three crater-like sinkholes and one cave of the huge system in the park are open to the public and they are truly memorable experiences.

The Arecibo Observatory is nestled in the mountains of northern Puerto Rico, about 30 minutes from Arecibo and is the world's largest radar/radio telescope. Here, scientists from all over the world use a giant 1000 foot (305 meter) diameter dish to listen to the universe. You may view the huge telescope from an observation platform, where its austere metallic symmetry shimmers in dramatic contrast with the dense, green, tropical landscape.Please note that this tour does include lunch or entrance fees at the attractions.