The Pentagon Renovation Program or PENREN was a long-term project by the United States Department of Defense to perform a complete slab-to-slab renovation of The Pentagon in Arlington, Virginia. The program began in the 1990s, and was completed in June 2011.The full-scale renovation became necessary because by the mid-1990s, the Pentagon had never undergone a major renovation, and building systems had deteriorated beyond repair, requiring complete replacement. Additionally, the presence of asbestos-containing materials throughout the building made any repairs or other work to the building highly disruptive.