Black cubic like object at first hovered and then ascended straight up until it became invisible, seemed to have gone/flown(?) right into space.I have been an amateur astronomer for almost 40 years. When a friend an I visited Rimini, Italy we never expected anthing like this.We have witnessed many things up in the air over there during daytime (like balloons and kite sailers), but this sighting happened after sunset and noone was near that place.When we first saw this (supposed) object it was bigger and completely black and (appeared) cubic shaped.There was no sound whatsoever.The whole event lasted about 5-7 minutesAfter a 3 minutes or so I took two pictures of the phenomena with a 60 mm lens (with about 1 minute in between).Pictures show the object definitely moved (straight up it seemed).There were (at least) 6 witnesses who regarded the object as being highly unusual (4 being Italians, both of us being Belgian tourists).Being a scientist I feel the need to report this, but I do understand very well this may be something very ordinary and that our eyes simply playing tricks on us.I was of course not prepared for something like this or would have brought a high zoom camera and binoculars.Maybe other reports can somehow confirm this sighting and that's why I post it. It's a UFO in the sense that I have no idea what this might have been.The closest thing I could think of being a candidate is a balloon of some kind ?