Rumored to be the famed pirate's lookout tower, this historic stone structure is now just watching for tourists.

A rare underwater observatory in the Caribbean that provides breathtaking views of vibrantly colored aquatic life.

A sharply wedged sundial marks the point at which each day in the United States begins.

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

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

The highest peak in Puerto Rico is home to a rare fern that can only be found on six trees at its summit.

This ''hidden'' 19th-century bridge played a simple, yet important role during the Spanish-American War.

This nearly abandoned "company town" is a ghost of Puerto Rico's once-lucrative sugar industry.

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

Invading U.S. troops were first seen from this now-abandoned tower, leading to the Spanish-American War.

A resilient tree that has survived for more than 700 years in Guánica Dry Forest.

Years of neglect and nature took a toll on this 19th-century lighthouse.

An enchanting natural wonder in Puerto Rico's Camuy River Park.

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

This giant bronze image of Christopher Columbus embarked on a voyage of its own.

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.

This sustainable, family-run farm just outside of San Juan makes for a dreamy daytrip.

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

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

On a clear day, you can see all the way to the Virgin Islands from the top of this observation tower built in the 1960s.

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

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