Gümüşler Monastery is the sight that lifts Niğde above an ordinary provincial stop. The complex is cut into soft rock in the village of Gümüşler, with a courtyard, rooms, passages, and a church decorated with Byzantine frescoes.
It feels related to Cappadocia's cave churches, but it is much quieter. If you have a car, it is an easy detour from Niğde; without one, ask locally about taxis or minibuses before setting out.