Federal Bureau of Investigation Headquarters, District of Columbia

The Federal Bureau of Investigation headquarters is in the J. Edgar Hoover building near the Mall in Washington DC. The FBI is the part of the US Department of Justice assigned to investigate many forms of unlawful activity and in enforcing federal law, domestically (though it does operate abroad as well). It has 56 domestic  field offices, located in major cities across the USA, and works with the dozen or so other intelligence and security organizations that are consolidated under the leadership of the Director of National Intelligence. The FBI used to give tours of the facility, consisting of a videotape presentation, a sharpshooting demonstration, and information on the history of the FBI, but not anymore. Much of the FBI's training, research, engineering, and analysis takes place at Quantico Marine Corps Base, in Virginia.