Howard Tunnel is supposedly the oldest railroad tunnel in the country that has been continuously in use. It says it on a signpost, so it must be true :) I believe the only train that still runs on this track is a scenic one for tourists, and it doesn't run very often. This rails to trails project is fairly unique in that the rails are in place and occasionally used!
The tunnel is roughly 300 feet long, and the interior is lined with bricks. Stones set into the walls proclaim that it was first constructed in 1840 and rebuilt with stone facings in 1866. I find it very weird to be able to see through the ridgeline!
This shot shows the brick surface of the barrel-shaped roof of the tunnel, along with the moss and other accumulations over the years. In several places small stalactites have formed. I guess its the calcium in the mortar that seeps through.