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

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

The world's brightest bioluminescent bay.

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

Legend tells how a Spanish soldier disappeared from this isolated sentry box without a trace.

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

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.

The ruins of the first Spanish settlement in Puerto Rico.

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

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

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

This 20th-century mansion plays a key role in one of Puerto Rico's greatest novels.

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

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

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

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

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

An unnatural lake in a naturally beautiful setting.

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

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

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

Puerto Rico's once thriving oil company is now an abandoned wonderland of rusty steel.

This community-driven organization uses education and eco-friendly technology to protect the environment.