In the early afternoon I was smoking and drinking a coffee in the terrace looking at the sky. There were some swallows flying in the summer sky and a hawk interested at them. The sky was clean and azure, except for a low soft cloud of some kilometers wide; height no more than a thousand meters from the ground. The sun was almost covered at the border of that cloud, so I could watch the sky and the hunt made by the hawk.Suddenly, I seemed to have seen a metallic reflection near the cloud. So I watched better at the sky, but I saw just a plane passing and the sun-white reflection on it. I thought it was that. But then I saw again another reflection near the cloud out of the corner of my eyes. So I began to gaze upon the cloud and after few seconds I saw a grey-steel metallic disk with a sphere inside of it, that classic UFO shape. That thing was visible for less than two seconds each time, was hovering like mad just below the cloud, performing curves similar to the boomerang path. Each time the object exited from the shadow under the cloud, I could see it for 1.5/2 seconds. Out of the shadow cloud the sun was reflected on it like in a common airplane. That white reflected on metallic surface. So I saw his crazy curved direction for a couple of second then became completely invisible, and some seconds after I saw it exited in another point of the cloud. And so on for almost 5 minutes. UFO was running around madly under that cloud, and even itself was rotating. Because was too fast and unpredictable, at a certain time I focused only on a side of the cloud so to see it clearly when passed.I was very impressed by its form, its agility and speed. It was totally out of place, nothing of natural, nothing of human. It seemed fake to my eyes because I had ever experienced under the sun such a strange thing. A perfect sphere dressed in a perfect disk. Elegant, amazing, charming, but in some way even terrible and wrong. I felt strange because of the implications of it on my life. I saw it clearly at least 4 times, and more than 10 out of the eyes corner. After almost 5 minutes, I stopped to see it. The way in which UFO became totally invisible let me with no words. Simply invisible from a moment to the next. And I wonder why each time the direct light of the sun hit the UFO, it became visible for a couple of second. Honestly now I saw clearly that they are here, but that invisibility can make me paranoid soon.What is interesting is that even the hawk saw the UFO. Near the beginnig, the hawk forgot about the swallows and went toward the cloud, flying always higher. When the hawk reached the border of the cloud remained stop up there for twenty seconds, that is, until the UFO appeared again from the cloud. After that, the hawk went down.Greetings.