Fan of Alcatraz Island? Many people are unaware that beneath the prison block at Alcatraz Island sits the foundation of an army fortification built in the 1850’s called the Citadel. Once four stories tall and surrounded by a dry moat, the fort was razed to the foundation in 1909 to make way for the current prison building. The Citadel was documented by the Historic American Buildings Survey (HABS) during the Summer of 2016 by HABS architect Paul Davidson and summer architectural intern Avidan Fernandez using a combination of laser scanning and photogrammetry. The animation was produced by Avidan, a summer intern from Cal Poly Pomona, whose position with HABS was funded jointly through the National Park Service Youth Programs and the Hispanic Access Foundation’s Latino Heritage Internship Program designed to engage the next generation of Latino conservation stewards. The project was jointly sponsored by a Cultural Resources Preservation Program Grant administered by National Center for Preservation Technology and Training (NCPTT), Golden Gate National Recreation Area and the Heritage Documentation Programs, NPS. The prison exterior and cellblock data was provided by the Texas A&M University College of Architecture. LEARN MORE See the HABS documentation of historic Alcatraz Island in the HABS/HAER/HALS Collection in The Library of Congress at https://go.usa.gov/xX3Dr Explore Cell Block D of the Main Prison Building by viewing this HABS panoramic photograph at https://goo.gl/UsPhFA Visit the Alcatraz Island National Park Service website at https://www.nps.gov/alca Information on the Latino Heritage Internship Program can be found at http://www.latinoheritageintern.com/ Read how Avidan spent his summer working HABS on his internship blog at http://www.latinoheritageintern.com/author/afernandez/