Archaeologists confirmed a long-time suspicion of historians and say that famed Alcatraz prison was built over a US Civil War-era military fortification.
Researchers found a series of buildings and tunnels under the prison yard of Alcatraz Federal Penitentiary, which once held Al Capone, SFGate reported.
A study published last week
in Near Surface Geophysics said archaeologists used ground-penetrating radar and terrestrial laser scans and historical maps and photographs.
They found fully buried structures, ammunition magazines and tunnels.
"This really changes the picture of things," study author Timothy de Smet, an archaeologist at Binghampton University, told PBS. "They weren't erased from the island — they are right beneath your feet."
