Although technically not a sound (it's a fjord), Doubtful Sound is the second longest in New Zealand-and the country's second most famous tourist attraction. It does, however, capture the top spot for being the deepest, at over 1,300 feet. Doubtful Sound sits at the far southwest corner of the country and winds its way for 24 miles, past small islets and lush mountains covered in dense, native rainforest. With a staggering amount of precipitation, up to 240 inches, it's no wonder that it's so verdant, and also why most days are wet and misty with low-lying clouds. But where there is rain, there are rainbows, which makes for spectacular scenes, especially at the many waterfalls, some of which fall over 2,000 feet. Doubtful Sound is also home to fur seals, crested penguins, bottlenose dolphin and whales. Black coral even grows here at relatively shallow depths (35 feet) thanks to the sunlight's inability to penetrate the top layer of freshwater, stained heavy with tannins from the forests.