Who designed Washington D.C. and what are some interesting attributes about the city?

Washington DC was designed by Major Pierre Charles L'Enfant at the request of George Washington.  L'Enfant was a civil engineer by training, from France, and based his basic design for DC on the streets of Paris.  DC is laid out as a grid, with east-west streets named alphabetically, starting with the letters themselves, and adding syllables as the streets went further out from the city center.  The north-south streets are numbered, increasing as they radiate from the Capitol.  At the intersection of the center-most streets are named for the direction as they radiate from the Capitol, i.e. North Capitol.  However, there is no West Capitol street, as that is the prominent plazas known as the mall.  Diagonally across the grid are streets named after the states and those state streets intersect in circles named after prominent Americans with plazas and open spaces.