This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

This beach pool offers a spectacle of crashing waves, blue hues, and a historical lighthouse.

This "sausage route" features gorgeous views and family-owned restaurants.

Enjoy the waters of this half-moon-shaped natural pool surrounded by breathtaking scenery.

Archaeological sites and great food inside the island's largest mangrove forest.

A natural swimming pool in the middle of the Carite Forest.

The short hike is worth the stunning views and crystal blue waters of a secluded beach.

This small fort played a huge role defending Puerto Rico’s capital city.

Legend has it this historic port was a popular hideout and smuggling spot for pirates.

On a small Puerto Rican island, banks of secret naval bunkers lie abandoned and filled with piles of office equipment.

A magnificent waterfall nestled in the heart of the El Yunque National Forest.

The world's second largest single-dish radio telescope, once used to contact E.T.

This former sugarcane transport tunnel is now a portal to a lovely beach.

This small primate research island is teeming with playing, fighting wild monkeys.

Rusting, graffiti-covered tanks litter the beach of this island, once used by the U.S. military for target practice.

The world's brightest bioluminescent bay.

Where a rare geological phenomenon created a section of rock that resembles a checkerboard.

All that remains of a magnate's dream home is a historic gate and an abandoned public pool.

A simple midtown bar was once the home of a secretive and exclusive club staffed by "bunnies" under Hefner's strict rules.

An enormous cat made of recycled wood scraps.

The first evidence of some of the Earth's earliest life was found in this fossilized undersea grotto.

The remains of a failed subway in upstate New York is now an underground graffiti bunker.

A museum devoted to bringing to light forgotten or neglected histories through exhibitions, education and public programming.

Tucked in the back of this amazing antique store is an important piece of medical history.