因为这里有一个主句和一个从句
主句是 Above the trees are the hills
从句是the river faithfully reflects on the surface.
而这个whose magnificence 作reflects的宾语
也就是 the river faithfully reflects whose magnificence on the surface.
也就是
the river faithfully reflects the hills’magnificence on the surface.
所以翻译为
树的上方是山 河水在表面映照出它的壮丽多姿