Land of Whirlpools

. Kushina Uzumaki was a kunoichi who hailed from this country. It is unclear if she was a ninja in a village located in this country or elsewhere. She came to Konoha as a refugee from this country. It appears the Whirlpool Country no longer exists as an independent entity, as it has been referred to in the past tense, as the 'former' Whirlpool Country.

Speculation
Due the lack of information, fans often assume that the major geographic feature is possibly likely multiple whirlpools and that "Uzumaki" might in fact be the major clan name. It is also very possible that most of the ninja mostly use Water jutsu as well, possibly whirlpool-based. Fans also assume that since "Uzumaki" means "spiral" or "whirlpool" that the Uzumaki's might have been the Daimyos of this country. This might also explain the spiral on the back of Naruto's jacket.

Trivia

 * Since the Whirlpool Country is referred to in past tense, it is possible that the country was destroyed though how or why is unknown. However, it is a popular assumption that it was destroyed in the Third Great Shinobi War, although this has yet to be confirmed.