Star Gates-Environment Design Concept

Set myself a brief to create a concept for a staple of the fantasy sci-fi genre, ancient monolithic star gates. If you haven't seen one of these floating in the background of your favourite science fiction game. You don't play games.
I started with a couple sketches with the usual ancient influences, but decided to go with something a bit more sleek. Something otherworldly and alien. Unknowable but functional.