There is much Masonic symbolism to be found in Washington DC, and some of it indeed is not apparent at merely a glance; however, this symbolism is not so esoteric as to be manifested in things like street plans. Sure, the streets are laid out in all kinds of neat designs and such - but things like six-sided stars and pentagrams are not Masonic symbols. Neither are owls or pyramids (I feel compelled to point out here that it's kind of intellectually dishonest to call a two-dimensional triangle, such as that in a street plan, a "pyramid", because it's not a pyramid, it's a triangle. But I digress).
Masonic symbolism in Washington DC is a bit more blatant than that. For instance, a stroll through the central hall in the Capitol building will bring to your notice several large paintings. Some of these paintings have smallish Masonic symbols in them - not so much "hidden" as merely inconspicuous compared to the rest of the painting's subject matter - things like trowels, levels, and squares (the tool, not the geometric shape).
There exists in Washington DC, I forget exactly where, a certain decorative covered well with a sculpture of a bird atop a square roof (I believe it's a pelican or stork, something like this). This is my favorite example of "hidden", yet blatantly unmistakable Masonic symbolism. There's nothing explicitly Masonic about the bird or the well itself, or even the form of the well. However, carved around the edges of the roof, are certain words - Faith, Hope, and Charity. Directly facing the side with the word "Charity", but across the street and some distance away, stands a small monument dedicated to something else entirely; however, on the front of this monument can be found the phrase "The Greatest of These is Charity". These words and phrases are taken directly from Masonic ritual, and cannot be interpreted as anything other than an explicit Masonic reference. Any Mason who actually caught these references would grin at the inside joke. As it stands, most people (necessarily including many Masons) just walk by these two minor monuments, paying them no attention, and never seeing the references.
But here's the problem. Squares, compasses, and levels are not sinister enough. Words like "Faith", "Hope", and "Charity" represent good notions, things that anti-Masonic folks would rather not explicitly associate with Masonry, despite their being lifted directly from Masonic ritual. If one truly wanted to indicate "hidden Masonic symbolism" in Washington DC, one could point to these references with complete confidence, yet they are ignored by conspiracy theorists in favor of vague and ambiguous symbolism, like streets arranged in star shapes. As mentioned before, six- and five-sided stars are not expressedly Masonic in nature. However, they are connected with Jews and Satanism, respectively - things which the conspiracy theorists have decided are linked with Freemasonry. Thus, in their mind, these symbols become "explicitly Masonic" references, and the street-plan of Washington DC becomes some diabolical Masonic plot. I am unsure what the conspiracy theorists think Freemasonry hoped to achieve through this sneaky design (as a rule, Masons have in the past been almost unilaterally Humanist/Enlightenment-types who simply did not believe in magic or hold superstitions tendencies), but there it is.
