Created from scratch, Washington (D.C.) was equipped with a geometric plan"à la française", drawn by the architect Pierre L'Enfant. This carefully preserved plan is accompanied by an exceptional"lower city" morphology in the United States. Washington is located along the Potomac, on the site of ancient marshes. The parallel and perpendicular streets are cut by oblique avenues which give on round places (circles). The Capitol, the White House, at one end of Pennsylvania Avenue, and the George Washington Monument form the three points of the"federal triangle. Along the coasts of this geometric figure are located departments, federal agencies, all official buildings. The originality of the city lies in its functions, almost exclusively administrative, the importance of research centres, cultural activities (libraries, cultural centres, universities) and the role of tourism, created by the constantly improved prospects, countless parks and green spaces, museums, the Capitol Hill, home of the U.S. Congress, the White House, home of the U.S. President, or the exterior of the famous Pentagon (in Arlington), symbol of U.S. military power. After experiencing a remarkable demographic boom in the first half of the 20th century (more than 800,000 inhabitants in 1950), Washington saw its population decline for fifty years (572,059 inhabitants in the 2000 census), to the benefit of its suburbs. The trend seems to have recently been reversed (588,292 inhabitants, 2007 estimate), in parallel with a gentrification of neighbourhoods previously subject to social problems and a significant decrease in crime, very high in the early 1990s. Of course, Washington, DC is a very interesting destination for those visiting the USA: there is the Capitol (where the Congress sits), the White House (where the head of state resides), the ministries, the national archives, the famous Pentagon (headquarters of the Department of Defense, which is actually located in Virginia, but so close to DC!), FBI offices, many museums, several memorials and monuments... from experience I can say that two days is not enough to see all the interesting monuments, even walking fast!