Precisely 104 degrees of longitude around the world west from Vatican City is…
…this spot in Tama County — approximately the intersection of Q Avenue and 370th Street. I had to zoom out for a landmark.
(I changed the “12” in the Vatican’s Google Map address to “-92”, and voila.)
Moved to scale, the loop freeway around Rome is in the area between Toledo and Holiday Lake in Poweshiek County.