We are travelling from Florida to Williamsburg,VA where we will be staying from 06-15-08 until 06-22-08. We will take day trips to DC and Philadelphia,PA during our stay. Please suggest MUST SEE attractions for these locations. We plan to visit the obvious places, i.e. Smithsonian, Library of Congress, the Mint, Elfreth's Alley Museum(?),Mt Vernon(?). Other suggestions, PLEASE.