ASD perception or something else

Hi, my four year old is non verbal with ASD. Sometimes he is frightened by things that he sees- eg double high sided walled path ( terrified) , nursery bathrooms with no windows, the lamp post that overlooks the back garden and the castle in the town we live. He loves nature and we are often in the woods surrounded by tall trees and he is happy with this. Is this an issue with perception , can someone please explain to me what he's seeing or if you have experience of the same with your little ones. He can run through a room littered with toys at high speed and not step on any and he can see a chocolate button from a mile off.