2000-10-29 - La Canada, CA - Triangle

My wife and I were sitting in the hot tub on our balcony when I spotted a very slow moving aircraft which I initially assumed was a helicopter. It was triangular, with non-flashing red lights at each corner and two large white lights near the center of the underside. The white lights pulsed on and off approximately every 5 seconds. When I tunded off the jacuzzi jets to listen to the craft, I realized that it was silent. My wife and I were rather amazed to see such a large craft (I'd estimate roughly 75-100 feet long by 50-75 feet wide) which made no apparent sound. I would estimate the craft to be about 400-800 feet above us initially heading from northwest to southeast and the disappearing only to return from the east horizon and heading west, practically passing directly overhead. It appeared to be travelling below the stall speed of most, if not all fixed wing aircraft (estimated speed at 35-45 mph) I last watched the craft about 5 miles away heading west over the city of La Crescenta, CA. As the craft passed over us, we heard a very soft rumbling or roaring sound.