An artificial crater field that trained astronauts for lunar exploration.

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

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.

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.

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

This tiny home was originally a narrow alleyway.

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

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

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

This niche museum devoted to ancient religious artifacts is shaped like the very thing it displays.

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

The bat-covered home of one of the world's most popular brands of rum is located on a tropical Art Deco campus.

This chapel on a cliff is renowned for its healing powers and was founded on the site of a supposed divine intervention.

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.

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

Largest man-made excavation on earth!

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

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.