The eyes of slugs are like a periscope. These can be retracted when threatened and come back out when the danger has passed. It is difficut for someone with eyes fixed in sockets to imagine what kind a view would be possible if they eyes were placed on an extension that can be moved independent of each other.
Thanks for all the comments on the Taj Mahal image, I am in the process of making an image gallery of my Agra visit. There are a lot of images and it will take time but hopefully it should be up soon.