Here are a few links to virtual tours of some famous buildings:

Washington, D.C.:

Library of Congress - Thomas Jefferson Building Tour

Smithsonian National Museum of Natural History

The Kennedy Center

U.S. Botanic Garden

U.S. Capitol (Senate) Virtual Tour

U.S. Supreme Court Building

 

Georgia:

Martin Luther King, Jr. Birth home

 

Massachusetts:

Harvard College

 

 Ohio:

National Museum of the U.S. Air Force

 

 Pennsylvania:

Gettysburg National Military Park

 

 Virginia:

George Washington's Mount Vernon

Monticello - Charlottesville, VA: Designed and built by Thomas Jefferson