Singapore (In Asia)11.8 million visitors

   (Just make sure you heed the local laws—something like spitting in the street might merely be considered rude in your hometown, but here, it carries a severe penalty.) You'll find historic sites like the Thian Hock Keng temple, superlative shopping (including gargantuan malls) and numerous beaches. Singapore is known as a bustling metropolis that also happens to be one of the cleanest and safest cities of its size in the world.