Archaeologists say they have found evidence that historians who have believed that the prison on Alcatraz Island was built over a Civil War-era military fortification are right.
According to a report in the SFGate, archaeologists discovered a series of buildings and tunnels under the prison grounds of Alcatraz Federal Penitentiary.
Those scientists published their finding in "Near Surface Geophysics" and say they used ground-penetrating radar and terrestrial laser scans and historical maps and photographs to locate the historic structures which included fully buried buildings, ammunition magazines, and tunnels. Historians have long suggested that it was considered easier to build over top of the military structures than to tear them down.
The United States government saw Alcatraz Island as a perfect location for a military installation due to its location in the middle of the San Francisco Bay.
Click here for more on the research into the underground history of Alcatraz.