Within the Kholin palace, the Circle of Memories is a round room with ten lamps on its walls, one for each of the ancient Epoch Kingdoms. An eleventh lamp - according to Lhan - represents the Tranquiline Halls.
They passed into the Circle of Memories, a round room with ten lamps on the walls, one for each of the ancient Epoch Kingdoms. An eleventh lamp represented the Tranquiline Halls, and a large ceremonial keyhole set into the wall represented the need for ardents to ignore borders, and look only at the hearts of men ... or something like that. He wasn’t sure, honestly.
From the description, this is - in fact - Kholinar's Oathgate, albeit nonfunctional, and the eleventh lamp is for Urithiru, the city of Knights Radiant to which each Oathgate once transported them. (Lhan's assumption might merely be misinterpretation, or forgotten history.)
That the Circle of Memories is part of a monastery means that, in all probability, the ardents housed therein live in facilities originally built for the local contingent of Knights Radiant. It's ironic that those who preach the betrayal of the Knights should live in their home and betray all that Vorinism originally stood for.
Outside the Circle of Memories, there is a walkway, between monastery buildings. The last leg of the walkways, even on a clear day, gave a wonderful view of Kholinar.