Sitting on my 3rd floor balcony at 10PM smoking my cigar facing SSW around 81st in Miami Beach, FL, I noticed a fast moving orb like object with alternating green and red lights. The object would hover, then move smoothly and quickly across the sky, travel east then west, north then south and descend on top of or behind a building located about 300 meters away across a small canal. The object made a slight humming sound when it flew closer. I am leaning towards some kind of advanced private or government drone. I have seen helicopters and planes in the area, this was nothing like the other aircraft. The event was weird enough to prompt me to post something here for the first time. The object finally disappeared behind or on top of a building and did not return. My only emotion was curiosity. Video is available.