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 near Rt. 66 and 340, Thornton Gap at Rt. 211, Swift Run Gap at Rt. 33, and Rockfish Gap at I-64 & U.S. 250. This is 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. Rockfish Gap Entrance Station is located in the souther end of Skyline Drive (Mile 105.4) and is accessible via I-64 and U.S. 250.
See the park website for entrance fees.