The Ahnonay Cathedral is an Age used by former Guild Master Kadish as an intermediary stop on the way to Ahnonay. The only accessible thing in this Age is a long corridor in an enclosed structure. This place was referred to as the "Ahnonay Temple" on the DRC's restoration project page.
As part of Kadish's efforts to prove himself as the Grower—a long-ago prophesied pseudo-religious figure with tremendous powers—he used this Age in conjunction with Ahnonay to fool people into thinking he could travel through time. Kadish would lead guided tours of Ahnonay, shuttling people back and forth between it and the Cathedral. The Cathedral's hallway is long enough that, once his guests had all linked away from Ahnonay, the rotating sphere mechanism there had enough time to rotate to the next "era" before Kadish's tour group linked back, giving the illusion of time travel.