I just released Nagaia Molag, a relatively simple quest that leads the player through a medium-sized Ayleid Ruin. The mod was designed to be extremely lore friendly (to the point of making some very obscure TES historical references and littering the place with translatable Ayleid text), and to fit seemlessly into Cyrodiil.
Description:
The call has gone out for experienced mercenaries looking to make some coin. An untouched ayleid ruin has just been uncovered at the mouth of the Brenna River, and the expedition set to explore it is in dire need of sellswords to defend workers and scholars from the unknown dangers of this long buried tomb. But while the expedition toils away, another force is at work in the long-lost depths of the Fire King's tomb.
TESA: http://tesalliance.org/forums/index.php?/files/file/1716-nagaia-molag/
Nexus: http://www.nexusmods.com/oblivion/mods/44936/?