If you have never visited the Abandoned Turnpike in Pennsylvania you are missing out. I try and visit there at least once in the Spring and once in the Fall every year. The Abandoned Turnpike consists of 13 miles of highway and two tunnels that were once a portion of the Pennsylvania Turnpike. When traffic increased to the point that the tunnels could no longer support it, the Turnpike Commission decided it would be more cost effective to bypass the tunnels. In 1968 the section was closed to traffic and became what is now known as the Abandoned Turnpike. Biking or hiking through Sidling Hill Tunnel (1.3 miles long) and the Rays Tunnel (0.7 miles long) are one of the biggest highlights of visiting the area.
I recommend starting on the Sidling Hill side of the Abandoned Turnpike and biking to the Breezewood side and back. The longer Sidling Hill Tunnel is only 1 mile from the parking area.