I was recently playtesting some mod changes in Windhelm when I found myself before Niranye's house. It was at this moment I realized I had never once been inside of this building, and curiosity getting the better of me, I used the console to open the door and have a look about. I was pretty stunned to find a hidden passage behind a sliding panel which led to a secret basemant. Therein was a safe with a note which told the rest of the tale behind the Summerset Shadows quest, which was quite a shock given the number of times I've completed the Thieves Guild questline.
Anyhow, this got me to thinking about all of the places I'm aware of but that I've never taken the time to explore. There are actually several houses in various settlements the insides of which I have never seen. I still haven't done the Whispering Door quest, and I only just entered High Gate Ruins for the first time this past month. That's with having had this game for nearly three years and having invested over 3000 hours into it.
So, what areas are you aware of yet have never bothered to explore?
Do you have a particular reason for not exploring some areas?
Are there areas you doubt you will ever explore?