The Skyline Drive runs 105 miles north and south along the crest of the Blue Ridge Mountains in Shenandoah National Park and is the only public road through the park.
You can enter Shenandoah at four places. Front Royal at U.S. 340; Thornton Gap at U.S. 211; Swift Run Gap at U.S. 33; and Rockfish Gap at I-64 / U.S. 250 (also the northern entrance to the Blue Ridge Parkway).
It takes about three hours to travel the entire length of the park on a clear day. Swift Run Gap Entrance Station (Mile 65.7) is accessible via U.S. 33.
See the park website for park entrance fees and other information.