Researchers found a series of buildings and tunnels under the prison yard of Alcatraz Federal Penitentiary, which once held Al Capone, SFGate reported Tuesday.

In March, we learned that archaeologists had discovered tunnels underneath the prison on Alcatraz — but they weren’t from potential escapees during the prison era.

A web of tunnels have been found under the grounds of Alcatraz Federal Penitentiary, but they were not used by prisoners who were trying to escape. Rather, experts say the tunnels and other buried ...

Researchers found a series of buildings and tunnels under the prison yard of Alcatraz Federal Penitentiary, which once held Al Capone, SFGate reported Tuesday.