Colorado National Monument is known for an elaborate system of hiking trails that wind themselves into and out of a number of rugged canyons, but the park's most famous and popular feature is Rim Rock Drive. Like Shenandoah's Skyline Drive or the Going-to-the-Sun Road in Glacier, this is one of those marvels of engineering that found their way into various national parks in the 1920s and '30s. The park service embraced a detailed philosophy of road-building in those days, assembling roads through difficult places for maximum dramatic effect. Rim Rock Drive achieves this as well as any road in any of the bigger parks. Designed in 1932, the road was built almost entirely by hand, using Depression labor employed in a variety of Franklin Roosevelt's alphabet soup agencies--the WPA, the PWA, the CCC. They still weren't done by the time the war started, but the government came back in 1948 and finally finished the road in 1950. The drive runs 23 miles, climbing 1,100 feet from the Colorado River valley floor in a winding series of tight switchbacks, dodging through a couple of tunnels bored through the sandstone by hand along the way, then twists along the edge of the rim of a seemingly endless series of canyons. Dozens of viewpoints along the way offer the chance to gaze into the abyss and contemplate gravity.