The national parks of the United States are visited by millions of visitors for their unrivalled natural beauty. What makes them truly unique in the world is that they range from tropical beaches to deserts and snow-capped mountains all within one country. These national parks are perfect spots to admire some of the country's most spectacular and geologically unique sites, or simply to hide away from the noisy world. It's hard to pick just a few of the US's national parks, but we've tried to highlight the 10 best for you.