This dungeon is your destination during side quest Forbidden Legend. It sits at the foot of the cliff that the capital city of Solitude rests upon. Loot the exterior campsite and then proceed inside.
Skill Book (One-Handed) Fire and Darkness - In the first open room, near an adventurer's corpse
Gauldur Blackblade - on the body of Mikrul Gauldurson
Gauldur Amulet Fragment (quest item in Forbidden Legend) - on the body of Mikrul Gauldurson
Word Wall (Frost Breath) - in the final chamber after defeating Gauldurson