I was doing the Halloween quest "commandeering a mortal vessel" and I couldn't believe my eyes! The mausoleus appears small, when you keep to the beaten track - but the place is titanic. I got lost and had to teleport out. What I found were entire lost Asura cities, strange anomalies, a mayan calendar, Ascalonian architecture, Stone Summit statues, enormous structures, murals dedicated to the six Gods (including Abaddon!) and much more.
Has this been found and documented yet? I took screenshots in case the answer is no.