While holidaying near Lake Como in Lombardo, Italy, Jolande van den Heuvel (Member 64,890) saw sky discs over the hills. Altocumulus lenticularis clouds like these can form downwind of raised terrain when airflows develop wavelike patterns after passing over the hills or mountains. At the peak of these invisible atmospheric waves, the moisture in the air can cool enough to condense into lenticularis clouds. If the wind speeds stay constant, the clouds remain fixed in place in the airstream. This means they can stay static even in the strongest of winds – hovering like silent observers visiting from another world.