*SPOILER* Potema's dungeon in Solitude was the hardest one I've done so far. The boss battle was so difficult. You start out fighting 2 Draugrs then everytime you win a fight, Potema ressurects the original two then adds a tougher Draugr. This goes on until you have to fight 5 Draugrs and a Draugr Deathlord. His unblocked attacks against my heavy armor were doing 120 to 150 damage. It really tests your durability.