Thanks for your reply, Greg. Too complicated for this old chap to attach a screenshot that way, email attachment would be easier! Anyway the black squares disappear when I uncheck "Ground scenery shadows", and as the shadows on, for instance, the static aircraft are beautifully modelled, I am completely happy with things now. Of course, if you can cure the problem in the future, I would be even happier! I have all settings maxed, except that Scenery Complexity is "Dense" and Autogen density is "Normal". Filtering is "Anisotropic". BTW, the strange squares are flat on the ground and conform