Alcatraz has a hidden fortress and tunnel system beneath it, scientists have discovered.
A team from Texas A&M University traveled to the former prison’s recreation yard, where prisoners would have spent as little as one hour a week, to see what lies underneath.
Using a ground-penetrating radar, the team found the remains of a military fortress which was thought to have been destroyed.
The team also found evidence of a subterranean tunnel system that would have been used as part of the fortress.
“(The tunnels) would have been used for the fortifications. There would have been movement of man and ammunition; it would have been bomb proof and covered with earth so it would have been protected,” professor Mark Everett told BBC.
The recreation yard.
What the team found.
“We get signatures that indicate there is not only a tunnel, but magazine buildings too.”
The structures date back to the 19th century, when the fortress was constructed after the gold boom in San Francisco turned it into a bustling port city.
The island also played a strategic role in the American civil way. However, the troops there didn’t see any action.
In the early 20th century the fortress was turned into an army prison, with the fortress being demolished or built over.
