I've been running Rise of the Runelords, Anniversary Edition for my group for a few years now (crazy). We're running up fast on the last adventure path, and I was reading about the Leng Device. According to p. 354, paragraph 5, "... numerous similarities between the stone ring at the center of the Leng Device and the much larger ring of stone located in the Varisian city of Magnimar--as if both devices were built by similar hands."
I'm wondering if this is an error, and the text was actually meant to say Riddleport. If I recall correctly, the Cyphergate's original purpose was to view the past, and the Leng Device has some functions along the same lines. I'm not aware of any large stone circles in Magnimar. If there is, someone please let me know.
I tend to think you're right.