Oddly enough, also in Rome there is the headquarters - basically just a building - of the Sovereign Military Order of Malta which many people believe to be an independent state, too. It
does issue passports, mints coins and issues postage stamps. It attended the original Geneva Conference and has observer status at the United Nations. I'm not totally convinced that it
really qualifies, but make your own mind up, after reading the material you'll find by clicking
http://www.worldstatesmen.org/Malta_knights.htm