The Space Man

I suppose the theme of my space man series was exploration. This exploration could be the physical act of going some place no human has ever been, or it could be some kind of self exploration. Who are we when we are truly alone? Are we our authentic self?

Here our protagonist is the most isolated human in existence, entire universes away from another person. It's just them and their trusty scout ship against the entire cosmos.

What are these strange structures? Who or what could have created them, and why aren't they still around?
If you have any theories feel free to post them in the comment section :)