I was taking a walk along with my dog at around 9pm last night. It was just getting dark, and the weather was clear. There are no trees or buildings near our farmhouse, and I could clearly see into the distant Flinders Ranges mountains.Suddenly, my dog started to bark, and I could see some flickering lights in the distance. First I thought it was an aircraft or a chopper, but then I realized the size of the object. It was huge. There were yellow lights on the three edges of the object, thats when I realized that it was something black and triangular. It was really big..I mean I could see it hovering near the base of the mountains some 10 kms away and the size was just enormous..I estimate it to be easily 100 feet plus. It was about the size of a 747, and it was hovering!! I could not believe my eyes. It stood motionless for about 5 minutes, then suddenly just lifted up and shot into the sky in a vertical motion. I couldnt believe it. I stood there for sometime trying to think what the hell just happened. I still cannot believe it. There must be some rational explination..but I'm hard pressed to find any. I have been living here for 20 years and have NEVER once seen anything like it.I dont know what it was but it sure as hell was not any conventional aircraft/helicopter.Hope someone can come up with a resonable explination.Cheers