Search the Antechamber of Uldum for an intact artifact.
I studied these ruins for years trying to find a way in. We even took a good chunk out of the gate, only to find impenetrable walls beneath. Now the cataclysm may've wrecked everything in there something fierce, but it's done what we couldn't and opened a way in!
I'd like you to have the honor, <lad/lass>. Head on in there and see if anything's been left uncracked. Be careful though... there's no telling what, or who, might be stirring in there.