ARCHAEOLOGISTS have uncovered a hidden military complex lurking beneath the infamous Alcatraz prison.
The mysterious structures date back to the 1860s, and were only uncovered after researchers examined Alcatraz island using hi-tech radar and laser scans.
Time Life Pictures Alcatraz was one of America’s toughest and most protected prisons
This map shows Alcatraz island, which sits off the coast of San Francisco
Years before Alcatraz gained notoriety as an offshore prison site, the island was a US military base.
Now researchers have uncovered new underground structures built during the mid-19th century that reveal the scale of military operations on the site.
Archaeologists at Binghamton University used laser scans and radar data to locate and assess long-lost structures lurking below.
The “nondestructive” research uncovered a buried architecture, including a “bombproof earthwork traverse”, a vaulted brick tunnel, and ventilation ducts, all of which ran east to west below Alcatraz prison’s recreation yard.
Binghamton University This image shows structures overlain on a map of the recreation yard
Binghamton University This illustration shows common military earthwork features that would’ve been at Alcatraz
Binghamton University Researchers used scanning equipment to reveal secrets lurking below
“I was surprised for several reasons,” said archaeologist Timothy de Smet, of Binghamton University.
“The remains of these historical archaeology features were just a few centimetres beneath the surface and they were miraculously and impeccably preserved.
“The concrete veneer of the Recreation Yard floor is incredibly thin and, in fact, in places sitting directly atop the architecture from the 1860s.
“We also learned that some of the earthwork traverses were covered over with thin concrete layers through time, likely to decrease erosion on the rainy windy island.
“It was wonderful to find the history just beneath our feet that we can visualise for the public.”
Binghamton University This is an exploded view of various scans – the green arrow points to communication tunnels found between underground traverses
Binghamton University This depth scan reveals various underground features captured from the surface
Binghamton University The red circles in the bottom right are underground ventilation ducts from concrete magazines beneath earthwork traverses
What is Alcatraz? History revealedHere’s what you need to know…
Alcatraz is an island 1.25 miles offshore from San Francisco, California
The island was originally developed for a lighthouse, but eventually became a military fortification and then military prison in the 19th century
And from 1935 to 1963, Alcatraz was used as the site for one of America’s most famous federal prisons
By November 1969, the island had become occupied for a group of Native American activists, who stayed there for nearly two years
And in 1986, Alcatraz was declared a National Historic Landmark, marking it as a popular tourist destination
Alcatraz is best known for being one of the toughest and most protected prisons in the USA
It was designed to hold prisons who were deemed the worst troublemakers at other federal prisons
Most of the prisoners were gangsters or murderers, and were known to be violent
Eventually the prison became too costly to run, so it was closed down in 1963
Alcatraz Island eventually became widely known for being a high-security federal penitentiary that housed America’s most notorious criminals.
But now it’s a tourist destination, with visitors flocking to see the site of the former prison.
However, the fact that Alcatraz also served as a coastal military fortification is largely overlooked by tourists.
Most of the military structures were destroyed when Alcatraz was converted to a prison, but researchers were able to uncover buried secrets below.
“During the construction of the now-infamous Alcatraz prison in the early 1900s, there was only one regulation and protection of cultural heritage in the US: the American Antiquities Act of 1906. And even so, Alcatraz would not have been considered under it, as it was so young and seemingly insignificant,” said de Smet.
“As such, the area was essentially bulldozed from the former military installation to the modern prison we see today.
Binghamton University By scanning with non-invasive methods, experts were able to find structures hidden underground without damaging them
Binghamton University Image (d) reveals buried ventilation ducts on these “3D depth slices” of the recreation yard
Binghamton University The yellow box on the top is the morgue, and the yellow box on the right-hand side is the remnant of one traverse’s magazine
Binghamton University The zoomed in areas of this recreation yard image highlight a traverse (left) and parapet wall of a battery (right)
“In converting the area to a prison, the vast majority of the previous military history of the island had been erased, but we wondered if perhaps something of that significant time in both the islands and American history remained, but buried and preserved beneath the subsurface.
“As such, we sought non-invasive, non-destructive means to ascertain if any historic archaeological remains lay beneath several parts of the island, like the Recreation Yard of the infamous US Federal penitentiary.
“We did not know what to expect. We did not know if there would be any extant subsurface architecture of these historically significant remains, or if there was anything left, what their extent and integrity would be like.”
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