Bing found the following results
The Pentagon - Wikipedia
U.S. Department of Defense
U.S. Department of Defense > Pentagon Tours
Pentagon History: 7 Big Things to Know - U.S. Department of Defense
Pentagon - Location, Building Timeline, 9/11 - HISTORY
Pentagon | History & Features | Britannica
PFPA | Visiting the Pentagon
Why Is the Pentagon a Pentagon? | Smithsonian
Pentagon summary | Britannica
DOD Websites - U.S. Department of Defense