Archeologists Uncover Buried Secret Beneath Alcatraz ‘So Close to the Surface’

By: Beth Moreton | Published: Mar 27, 2024

Most people are likely familiar with Alcatraz Island and the prison, but it turns out there is more history on this island than meets the eye.

Archeologists have recently found some tunnels and buildings beneath Alcatraz, but there are still questions as to how they got there. 

Alcatraz Island Is a Popular Tourist Destination

Alcatraz Island is located outside of San Francisco and is directly opposite the Golden Gate Bridge.

Alcatraz Island at night. The island is lit up and there is fog surrounding it, which makes it difficult to see anything in the distance.

Source: Unknown Author/Wikipedia

Alcatraz Island Tickets states that you can do day and night tours of the island, as well as a behind-the-scenes tour, with tickets starting from $35. 

Alcatraz Island Has a Military History

Alcatraz Island is more commonly known nowadays for its prison, but it is shrouded in deep military history.

A black and white image of Alcatraz Island when it was a military base. There is a port at the bottom of the island and various houses up on the hill.

Source: Unknown Author/Wikipedia

The military was given control of the island in 1848 and ended up building a secure prison there, according to Trend Chaser, which became one of the most famous prisons in the world.

Alcatraz Island Was an Important Moment in History

With its military history being prominent, the buildings on Alcatraz Island while it was a military base marked an important moment in history.

A black and white image of Alcatraz Island when it was a military base. The lighthouse is visible, as well as a few other houses at the top of the island.

Source: Unknown Author/Wikimedia Commons

The buildings built during the 19th century show the transition from traditional brick and masonry constructions to earthen structures, according to

Alcatraz Island Was Discovered in 1775

When California was under Spanish rule, Alcatraz Island was discovered in 1775 by Spanish naval officer Juan Manuel de Ayala.

A black and white photo of Alcatraz Island before the prison was built. There is a jetty at the bottom of the island and various houses and other buildings are built along the island.

Source: Unknown Author/Wikimedia Commons

He originally named it La Isla de los Alcatraces, which was later changed to Alcatraz Island. This translates to the Island of the Pelicans in English.

Alcatraz Prison Had Many Famous Prisoners

Alcatraz prison had many prisoners from the 1930s through to the 1960s.

A black and white photo of Al Capone. He is wearing a suit and has a neutral expression whilst looking off to the side of the camera.

Source: Chicago Bureau/Wikimedia Commons

Some of these were famous, like Al Capone, George “Machine Gun” Kelly, and Whitey Bulger.


A Study Discovered the Land Beneath Alcatraz Prison

A study published in Near Surface Geophysics was able to discover the tunnels and buildings beneath Alcatraz prison.

Alcatraz prison in the recreation yard. The yard is mostly dirt and has some steps leading up to the prison behind it. There is a barrier of high walls all around the yard.

Source: Radomianin/Wikimedia Commons

They used ground-penetrating radar data along with terrestrial laser scans, historical documents, maps, and photographs. 


Electromagnetic Waves Were Used to Discover the Architecture

Archeologists were able to discover the architecture buried underground from the use of electromagnetic waves.

An image of an electromagnetic wave. There is an X, Y, and Z axis and two waves. The blue one is the magnetic field and the yellow one is the electric field. The electric field goes up and down, whereas the magnetic field goes up and down at an angle.

Source: Leah Hustak/Wikimedia Commons

According to PBS, a radar is used that puts electromagnetic waves into the earth and this returns signals that show exactly what is buried underneath the ground without having to dig anything up. 


Buildings and Tunnels Were Discovered Underneath the Recreation Yard

The majority of the tunnels and buildings were discovered under Alcatraz prison’s recreation yard.

The Alcatraz prison recreation yard. The yard is made of concrete and some hills can be seen in the distance. There are some people in the yard and the high walls surrounding the yard make it hard to get out.

Source: Steven Lek/Wikimedia Commons

They were able to find a bombproof earthwork traverse, a brick masonry tunnel, and some ventilation ducts.


The Remains Are Directly Beneath Your Feet

The remains are not only buried underground, but they are also so close to the surface and so well-preserved that they practically touch your feet, according to Binghampton University.

The Alcatraz prison recreation yard. The yard is made of concrete and has a high wall surrounding it so no one can get out. There are some hills in the distance covered by clouds.

Source: Jester7777/Wikimedia Commons

They were also covered with thin layers of concrete over time, which means the likelihood of erosion had decreased, meaning the structures had been perfectly preserved. 


The Archeological Findings Are a Good Example of Modern Technology

Due to the non-invasive nature of the technology used to discover the tunnels and buildings, archeologists have said it’s a good example of how far technology has come.

The Alcatraz prison recreation yard. The yard is a mixture of concrete and grass and is surrounded by steps to get down to it and a high wall around it, with the prison in the background.

Source: Crazyrachle/Wikimedia Commons

It helps to answer many questions about things such as human behavior, social organization, and cultural change, all without causing any damage. 


More Archeological Digs Have Been Planned on Alcatraz Island

With these findings now in place, archeologists are supposedly planning on carrying out more research on Alcatraz Island in the future.

Alcatraz Island. The prison is at the top of the island and some hills can be seen in the distance behind it. The island is surrounded by blue sea and a lighthouse is in front of the prison.

Source: Don Ramey Logan/Wikimedia Commons

They believe there is still a lot more to be learned about the island, and will likely carry out more non-invasive research techniques to discover what else may lie beneath the famous prison.