2. Ottawa River, Canada

( ibackpackcanada.com )

The Ottawa River does a lot more than distinguish the border between Quebec and Ontario. The behemoth waterway is also Canada's most popular destination for rafting and kayaking. Luke-warm waters attract families and die-hard rafters each summer to steer through a valley thought to be more than 175 million years old. Take the kids for a leisurely paddle, or put on helmets with more competitive friends and race down the wondrous archipelago at top speed.