The hallways of the
Horus are cramped and dark. Spacers get used to dim red emergency lighting for most purposes. Warships do not need to look pretty, so much of the space and effort that would go into aesthetics or cowlings is put into other areas.
Exposed cables and pipes crawl over head and the deck is a mere grate in many cases. Access and electrical panels line the walls. Some of this is intentional: Anyone who gets aboard the ship who doesn't belong there faces lengthy, narrow and confusing hallways, separated by strong hatches and bulkheads. The extensive infrastructure is redundant across multiple access-ways and makes it hard for someone in an assault suit to march two abreast around the ship, forcing boarders to line up against defenders.
The hallways serve one more important purpose: This is where you go to speak when you need privacy. Most of the time, hallways are clear unless someone is heading somewhere in specific.