During World War II the small island of Vieques was nearly completely overtaken by American naval forces who occupied either end of the narrow stretch of land, and today the hidden bunkers they built still remain, abandoned and full of detritus.
Lying just off the coast of Puerto Rico, Vieques sits in a position that became of strategic importance after America joined WWII. Purchasing 2/3 of the island in 1941, the US Navy built a training facility on the Eastern end and a series of hidden concrete bunkers on the Western end, leaving the middle of the island for civilian use. The bunkers were used to store weapons and ammunition, and they were built right into the natural contours of the island so that anyone viewing the complex from the air would simply see a series of hills.
After the war, the military continued to use the island to store, and far more devastatingly, test their armaments, causing untold damage to the ecology and communities on the island. Thanks to repeated protests the armed forces agreed to pull out of the island in 2003, leaving behind not only their permanent bunker system, but countless unexploded bombs that are still being found today.
The remaining bunkers now stand empty and abandoned. Some of them are still closed and locked, but many lie open exposing piles of computer monitors and other remnants of their operation. The military sections of the island are still restricted due to the prevalence of hazardous munitions, but the bunkers remain, waiting to be explored on the day the clean-up is finally finished. The cleanup is currently being taken care of by the US National Fish & Wildlife Services.