This building is called the Pentagon. It is in Arlington County, Virginia. That is near Washington, D.C. The building gets its name from its shape. A pentagon has five sides.
The Pentagon is a United States government building. The Department of Defense is based there. The Army, Navy, and Air Force have headquarters there. The Pentagon was built between 1941 and 1943. President Franklin D. Roosevelt was involved in the planning.
The building is huge. It has thousands of windows. And there are more than 17 miles of corridors. There is more floor space than in most skyscrapers.
But it is easy to walk around the building. That is because of its unique design. It takes seven minutes to walk from one side to the other.