I found about 5 or 6 whilst randomly dungeon diving. I was going through my phase of completely and utterly failing to complete quests because I was being attracted, moth-like, to every ruin, cave and fort that popped up on my compass.
*scooting along, undiscovered location pops up on compass*
"Oh, I spose I'll get close so I can fast travel to it later"
*gets close and has it marked*
"Hmmm, now I'm here, I I should stick my head in quickly, see what its like"
*enters*
"Oooh, whats behind this door/down this passage?"
*fights first enemy*
"Well, now I've killed something I may as well do the whole dungeon"
Repeat ad infinitum.
