This small-town library was the first in the world to be entirely supported by taxation.

Stumps of an Ice Age forest, visible only at low tide.

A place to pay homage to Taíno heritage.

This beachside town is home to a diverse nature reserve, multiple cays, and one of the three bioluminescent bays in Puerto Rico.

The world's brightest bioluminescent bay.

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

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

This museum preserves the heyday of Puerto Rican coffee.

Built some 700 years ago, this Taíno ceremonial site features ball courts, petroglyphs, and evidence of ancient astronomy practices.

This former railroad bridge was named after the great river that once flowed below it.

An unnatural lake in a naturally beautiful setting.

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

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.

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

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

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

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

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

This colorful gate stands as an entrance to the walled city of Old San Juan.

This tiny home was originally a narrow alleyway.

The crumbling remnants of this 19th-century quarantine hospital hint at the touristy island's darker past.

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

Puerto Rico's oldest rum producer started its 140-year-old business with "a little barrel."