@Guroga @ojoudere
In the novel, the dungeon was a relic of a warring period and was specifically meant to hold noble prisoners. It had all the basic facilities but was unfurnished and furnishing was given depending on how the royalty wanted to treat the prisoners. So there were times when it was extremely well furnished with plush rugs and beds and times when it was just bare stone floors.
The dungeon has running water and a water system that, according to the novel, if carelessly damaged and destroyed to block the waterflow to the dungeon, could result in flooding half the castle. It was also set up so that it had a bath, a toilet, and a sink. Rachel prepared though and put up screens to make the bathroom area a nice private area, brought in lamps, furniture, tapestries, rugs, food, expensive drinks, books, comfortable clothing, and well, just a ton of things for entertainment and comfort.