Map by John Till (w. Rachel Kronick) based upon Professor Barker's original.
I've inserted into the map I'm making and scaled it - somewhat arbitrarily - so that the distance between the two end towers of the south wall was 3 kilometers. This seems to look OK next to the other cities I've inserted. When I checked the width of the river the narrowest section comes in at around 50 meters, which I think is in keeping with the comments Professor Barker made about the Ranánga river on the Blue Room mailing list.
And today I was flipping through my copy of the Deeds Ever-Glorious (that is, the histories of the Tsolyáni legions, available from RPGNow.com - and well worth the price!) I discovered an interesting reference under the Legion of Chegárra, the Hero-King.
Actually, I think Thráya is mentioned several times throughout the histories. That book truely is a "must have" for Tékumel fans. There is loads of non-military information included and I found it gives a good insight into how things "work" in Tsolyánu.