The valley is closed to the north by a high plateau that joins these two mountain ridges, but is open to the south at the southern terminus of Mount Nittany.

The Keystone Shortway, now Interstate 80, runs diagonally across the Nittany Valley on a west to east line, from Curtin Gap east of Milesburg, Pennsylvania, to a natural gap in Mount Nittany and then via a deep rock cut along the Long Run stream.

The Nittany and Bald Eagle Railroad short line spur that enters the valley from Milesburg, then runs along Spring Creek to Bellefonte, splits, with a track going northeast to Pleasant Gap and another going southwest to Lemont and State College.

During the Appalachian orogeny, the sedimentary rock layers folded up into the Nittany Arch anticline.

The oldest rock layers from deep within the eroded mountain are now exposed on Sand Ridge in the middle of the valley.