Even if you aren't tempted by Sin City's allure, Las Vegas can be a relatively cheap and easy place to start a trip to other parks in the Southwest.
The Grand Canyon, the granddaddy of them all, was the second-most visited national park last year, and it's no wonder why. A mile deep and sometimes 15 miles wide, with rock layers of all colors going back 2 million years, it overwhelms with its immensity.