Rationalwiki debunks the DC city design myth saying:
The claims about the D.C. street layout are easily refuted just by looking at an actual map of the city. Conspiracy literature will show Rhode Island Ave., Vermont Ave., Massachusetts Ave., Connecticut Ave., and K Street making up five lines of a pentagram. A look at the actual street map shows that Vermont and Connecticut Avenues do not extend south of K street so there is no point below that, and ergo, no bottom point of any pentagram pointing at the White House. Further, Rhode Island Ave. does not extend west of Connecticut Ave. so not only does this alleged “pentagram” not have five points, it doesn’t even have four. It is purely the product of someone’s overactive imagination.
As to whether Masonic symbols such as the square and compass can be found in the street layout, this would seem to be conceivably possible given that many of the Founding Fathers were Freemasons. In actuality, the city’s street layout was designed by Pierre Charles L’Enfant, a French-born architect appointed by George Washington and Thomas Jefferson to design the city. L’Enfant’s design somewhat resembled that of Karlsruhe, Germany. But even if Freemasonry was an influence on the street layout, so what? Most street intersections everywhere resemble a Christian cross – is this evidence of a Christian conspiracy to control the world?
There is also the question of whether symbols and buildings can somehow harbor or channel demonic forces, witchcraft, or other supernatural powers, solely because of their design. This is one nutter belief piled on top of another; one has to first believe in the supernatural, and then believe that man-made things can have the power to harbor or channel that supernatural, and then further believe that this can somehow place an entire city under occult control or provide a direct line of communication between Satan and the President of the United States. This is all patent bullshit.
Finally it should be remembered that Washington was a planned city. The street designs were intended to be laid out on a diamond shaped grid with both numbered streets and streets named after letters intersecting them. Traversing the whole city are streets named after various states and figures in American and local history, running on diagonals. As a result things that look like pentagrams, Masonic t-squares, and compasses in an overhead view were inevitable. Finally, there have been many changes and revisions to L’enfant’s design as the city has grown over the years.