What we have here is a donjon that is lived in!
Games these days often have a functional setting. Buildings are often layed out not first as buildings, but as levels. The net result is that the player doesn't become terribly interested in the setting, but is just focused on getting from point A to point B.
In some ways, this makes sense. We don't want to bore the user with endless corridors, or too-regular level designs. At the same time, there is something to be said for creating a world that feels like it has a backstory to it, that is inhabited by other creatures and not just created for the player's sake.
I tend to create the setting first, and then put the gameplay into it. Besides having a general idea for gameplay elements I might like to create, my goal is to try and create a setting that should support the kinds of ideas I already have for my game, without being too specific. So the "room where you use the mirror to reflect the beam of sunlight onto the idol to unlock the chamber housing the serpentine gauntlet" is not a great place to start; rather, I try to think about what interesting places there might be to visit in a certain area. In The Real Texas, there is a mine. Abandoned mines are about as unique an idea for a videogame setting as haunted castles, granted, so it hasn't a chance of flying on it's own. Some notable videogame mines:
Back to my game. I don't want to give it totally away, but basically there is an area you can go to and it's like there was a bit of an underground keep, from some lost age. In one room, is an altar with an evil pig face on it, and a tattered rug. Other rooms will have old bed frames, mattresses, that sort of creepy stuff.
I'll figure out what relevance it all has to the game later on. Also if you look at that picture closely you'll see the main character is wearing his underwear overtop of his pants. Awesome.
Now for an amazing story: one time, a friend who did construction told me about visiting a local co-op grocery store basement. They were refinishing the basement, or something, and in the process had to rip out some drywall. It turns out that at some point in the store's history, they had drywalled right over a doorway, which led to a cafeteria. The cafeteria itself was fully furnished, with tables and chairs and kitchen equipment still put away as if the staff had intended to come back the next day. Creepy, and cool! He took an antique milkshake maker from it.
So it turns out that even in real life, sometimes you really do get to travel into dungeons, find secret doorways that lead to mysterious, long-abandoned chambers filled with fabulous treasure, and take some home.