I was with a girlfriend at the dock yard of the Cherry Creek reservior. The object was a black triangle. I noticed it flying low in the sky. It was broad daylight. No clouds. It flew in from the West, banked and turned at sharp angles rapidly. It flew directly above me and made no sound at all. Then it flew back into the West and landed at a fast 45 degree angle behind some trees. The landing site was several miles away, so the object had to be very large. When it landed, it wasn't flat, but the points of the triangle were up and down. I was really amazed at the object and didn't now what to make of it. It had no discernible tail, cockpit, or any bulges or lumps. It was very close, but there were no windows, lights, or appendages.