I got one courtesy of this site for the Book of the New Sun. The narrator discusses a guild of beast trainers, and gives the detail that supposedly they forsake women and take animals as spouses. While this actually wouldn't be too odd, since there is also a guild of torturers, the fanon theory that the narrator was confused about the term "animal husbandry" makes a lot of sense, given that there are several other Future Imperfect examples in the novel.- Jordan
The purpose of the great wall at Thrax only became apparent to me on a second reading of the novel. The wall is actually the face of a large hydroelectric dam. Everything Severian describes about Thrax (the city of windowless rooms, since it is in a gorge and uses the abundant hydroelectic power for lighting) is consistent with this explanation. The jail is in one of the now unused bypass tunnels for the dam. Severian describe everything accurately but is to uneducated to really understand it. Lake Diaturna is the reservoir behind the dam.