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

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

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

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

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

The ruins of the first Spanish settlement in Puerto Rico.

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

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

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

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

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

This perfectly preserved Chinese medicine shop was untouched for decades before being reopened as a museum.

Abandoned landscape once home to "the world's largest winery."

Once the largest winery in the world, this castle-like building now sits abandoned on the San Pablo/San Francisco Bay shore.

A brooding mansion of clinker brick stands out among the Victorian houses of Pacific Heights.

Historic home to one of the most famous women pioneers of the 19th century.

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.

Failed state-supported institution meant to rehabilitate students with intellectual disabilities.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

A Turkish ghost town abandoned in a population exchange with Greece.

A toxic ghost town sitting atop a massive coal fire.

Crumbling pink walls and murder memorials preserve the pioneer history of Joshua Tree.

The remnants of a failed socialist commune can still be found just off a California highway.

A New England-style lighthouse along California's beautiful Highway 1 gets a re-do.