A view of Alcatraz Island from the ferry on arrival (Photo credit: Ian Whitworth/Dreamstime)

(Photo credit: Ian Whitworth/Dreamstime)

Archeologists Find Hidden Tunnels Below Alcatraz

March 6, 2019

SAN FRANCISCO (AP) — Archaeologists have confirmed a long-time suspicion of historians and say that famed Alcatraz prison was built over a Civil War-era military fortification.

SFGate reports researchers have found a series of buildings and tunnels under the prison yard of Alcatraz Federal Penitentiary, which once held Al Capone.

In this July 7, 2011, file photo, Jim Breeden of the Golden Gate National Parks Conservancy, walks through the dungeons below the main cell house during a night tour on Alcatraz Island in San Francisco. (AP Photo/Eric Risberg)
(Photo credit: AP Photo/Eric Risberg)

A study published in "Near Surface Geophysics" says archaeologists used ground-penetrating radar and terrestrial laser scans and historical maps and photographs.

They found fully buried structures, ammunition magazines and tunnels.

Historians believe workers built over existing structures when the prison was built in the 20th century.

In this July 1, 2015 file photo, people walk through the citadel, also known as the the dungeon, during a tour of newly restored areas on Alcatraz Island in San Francisco. (AP Photo/Eric Risberg)
(Photo credit: AP Photo/Eric Risberg)

Alcatraz first came to the attention of the U.S. government after it wrested control of California from Mexico in the 1840s.

Its location in San Francisco Bay made it attractive for military fortification purposes.