Two-Sun

 is a city deep in Caesar's Legion territory.

Background
Two Sun is all that's left of the Arizona city of Tucson. Raul Tejada claims to have lived there for 75 years after the bombs fell, but left before the arrival of Caesar's Legion.

Raul also makes a big deal about the pronunciation and spelling of the name of city. This may be because he is the only person who knows(or cares) about it.

Appearances
is mentioned in Fallout: New Vegas.