There was Once a Major Canal Along the National Mall

An 1862 map shows that the Washington City Canal ran along the north side of the mall, on what is today Constitution Avenue, toward the site of the Capitol Reflecting Pool (the Mall itself was much smaller, ending at the site of the Washington Monument):

This is a view from the Capitol Building looking West, you can see the Smithsonian Castle at center-right and Maryland Avenue SW at the left:

It existed from 1815 to 1871, when it was filled in. Here's another, illustrated, depiction:

A New (Photoshopped) Look at the White House Situation Room Photo

Maybe now we know why Hillary Clinton's hand was at her mouth: 

The above was made by my sister, Charlotte. Check out her real photos on her flickr photostream here. And if you liked this, check out her Charlie Sheen Meets the Parents Video.