Gallifrey from Doctor Who TV Series is popular as are real places where people live like USA, New York, London, Liverpool etc.
However if you decide just to go with the default name given by the game of "Rising Sun Valley" then you will be joining a league of people who seem to number in the high thousands with absolutely no imagination and who are impossible to tell apart during trading on the Global Trade HQ making it like Ebay with the scams but without the warning signs of a bad reputation.
I swear that nearly every Rising Sun Valley that advertises items for sale always ends up being an empty dead-end depot if I ever waste a click on them:
