The Hidden Waterfall Village is a very small village that we've only seen in Naruto's Jump Festa 2004 so far. Because this village is so small and has very few (strong) shinobi, it's build behind a Waterfall - hence 'The Hidden Waterfall Village'. Only its inhabitants know the village's entrance.
The Hidden Waterfall Village has no Kage, but they have something called the Hero Water to help them protect their village. It's some sort of holy water which is extracted from the great tree (located in the Hidden Waterfall Village) every one hundred years. It is suposed to tenfold the user's chakra, and aid the 'heroes' in protecting their village in times of battle.
However, this water is a double-edged sword, altough it increases one's chakra, it also eats away your liveforce at the same time. Only the young ones (most of the time younger means weaker, strength grows with experience) will be able to survive the side effects of the water. For that reason, many of the village's shinobi have died not from battle, but from the water.
The holy water is sealed away, and it's the village's leader's duty to protect the Hero Water at all cost. The village's leader is also called the Hero of the Hidden Falls, but the question remains: 'Would you drink the Hero Water and throw away your life, just to save your village and be remembered as a hero?'.