怎么样区别此题中的seeing与seen

______ these pictures, I couldnt help thinking of those days when I was in Beijing and ______ from the TOP of a thirty-storeyed building, Beijing looks more beautiful.
答案是seeing, seen。我的答案是seeing, seeing。为何啊？谢谢！

第一空应填 Seeing，由于它的逻辑主语是I，而I与see为主动关系，故用目前分词seeing；第二空应填 seen，由于它的逻辑主语是Beijing，而Beijing与see之间为被动关系，故用过去分词seen。句意为：看到这类照片，我不不由自主地想起了我在北京的那些日子。从一栋30层高的建筑物顶层看去，北京看着更漂亮了。