U.S. President Donald Trump's plan to convert Alcatraz back into a maximum-security prison could cost roughly $2 billion, Axios reported on Friday citing administration sources.

Federal officials recently visited Alcatraz as part of the president's efforts to reopen the historic site as a prison. How did we get here?

Trump administration officials have toured Alcatraz, the once-notorious prison island in the icy waters of San Francisco Bay that the Trump administration is seeking to re-open for prisoners. Alcatraz - popularly known as "the Rock" - has not been used as a prison for decades. It is now a historic landmark visited by millions of tourists each year.