From the fringes of New York to the heart of steamy Singapore, nature is everywhere you're not looking in some of Earth's most notoriously crowded big cities. From river walks to mountain peaks and everything in between, outdoor adventure is often just a few stops on the train - or a short drive - away from the maddening crowds.
Here are a few favorites to get you going:
-Mount Hollywood Trail, Los Angeles
It's not a skyscraper or a Ferris wheel. It's not the Eiffel Tower and there's no pricey circulating restaurant up top. But if you want an absolutely unforgettable, no-admission-charged, 360-degree view of the entire Los Angeles region - the valleys, the mountains, the...