Titan is the most atmosphery moon in the Sol System. it is by no means a terrestrial class A moon, however, it can be adaptable, and possibly terraformed. On Titan exists a lot of Saturn's attractions, including the saturn museum, and the observation station.
Recent discoveries lead to the finding of a small interstellar race that has formed a society on the moon thousands of years ago. They lived in two domed cities near the sout pole of the moon.