Lincoln Caverns was discovered in May 1930 by a [PRBREAK][/PRBREAKroad crew building U.S. Route 22. It's an amazing underground experience.]
If you go:
Trail leading to Whisper Rocks where you go first it steep and uphill, Wear sturdy shoes. They are open seasonally and offer different events during the year. Check website.
Links:

7703 William Penn Highway / U.S. Route 22
Huntingdon, Pennsylvania 16652 USA
Phone Numbers:
Office
+1 (814) 643.0268
+1 (814) 643.0268