At the top of the container is

Hi, I have just read the sentence below and found it somehow problematic

At the top of the container is a lever and attacehd to the lever there is a thin, extended pin.

My questions are:

1) [At the top of the container] is a prepositonal cl. used as an adverb in the sentence, so why [At the top of the container] is followed by [is] and functions like a subject? Is it grammatically correct?

2) [Attached to the lever] seems to be used as the subject following by [is a thin, extended pin], is it possible? It sounds weird to me.

Thanks