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

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

This memorial to a family's dead son has survived a century of hurricanes and earthquakes.

These red and black houses were awarded to the firefighters who saved their city from an enormous blaze.

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

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

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

The ruins of the first Spanish settlement in Puerto Rico.

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

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

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

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

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

The abandoned remains of this once-thriving hotel looms over the city, awaiting an uncertain future.

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

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

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

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

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

This tiny home was originally a narrow alleyway.

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

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

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

The location of Puerto Rico's first water bottling plant, thanks to a collaboration between Mother Nature and technology.