Was on the pool deck of an apartment complex, unobstructed view of sky, just east of liberty memorial, we were looking south west at the air space over the south end of liberty memorial and in front of the federal reserve building. object came out of the west flying fairly straight east with some swoops and alterations of latitude. mimic'ed a bird in flight to some degree--i thought at first it was a bird but at such a high altitude and solid shape, it caught the eye. no wings, no tail, solid disc shape. 1.5 to 2 foot in diameter. looking closely, it glinted silver and caught the light on one side--silver/the other dark in shadow. no lights, no rotors, no arms. i thought it must be a drone at first as that is a popular place to fly them--but it didn't circle back at all, no jerks, very smooth movement though following a curvy flight path. it was like a bird in it's up and down motions, not jerky or straightly vertical in it's ascents and descents. was clearly not a bird though moving like one. it flipped and swerved and maneuvered--it did not tumble, it was a constant, smooth velocity through out. it disappeared out of my sight line behind a very tall office building, i looked for it to come out the other side--but it must have flow south at that point, or south slightly east as it never appeared again. i am reporting it because it may have been doing some sort of reconnaissance over the federal reserve. it flew smoothly due east with some flourishes in the air space to the north of it, in front of it, not so much directly over head of the building and it did not stop or hover at all. i tried to get a picture of it on my phone but it would not show up on the view finder, that could have been angle and distance, who knows.