built a temple on top of it .On the top they ……1句top前没加the而2句却加?

问题描述:

built a temple on top of it .On the top they ……1句top前没加the而2句却加?
原句前半段They built a pyramid and then
那什么时候加呢

on top of是顶上的意思
on the top of是在顶部的意思
和in front of,in the frong of是相同的用法