over的基本含义是:higher than something,without touching it(高于某物,没有接触)如:A lamp hung over the table(一盏灯悬挂在桌子上方。).还可以表达on something or covering(覆盖在上面):She wore a large jacket over her sweater(她在毛衣外面穿了件宽大的夹克).注意这个句子,一件宽大的夹克把毛衣都覆盖了,也就是讲把毛衣各处,如毛衣袖子,领子,前部,后部都覆盖了,于是就有in,or to many parts of a particular place,organization or thing(到处,各处),结合这里的语境,就是带他到南京大桥各处看看,参观。