Managers say they have never seen anything like it before
Underground icicles have formed 200ft beneath Matlock's Heights of Abraham, giving the caverns a complete facelift.
The huge ice spikes - some measuring up to 6ft - appeared during the cold spell in December.
The caves don't feature stalagmites or stalactites and managers say they love the new look the icicles helped to create.
The biggest example was found in the Great Rutland Cavern and had a diameter of around 30 inches.
Heights of Abraham's John Armstrong-Coulson said: "Normally the temperature is a constant 7C in summer and winter.
"This year with temperatures outside dipping to -15C or below, the airflow through here has seen a significant change in temperature.
"We've occasionally seen one or two icicles at the entrance to the cave in the past.
"But with the melting snow and the huge drop in tempeartures we've had what has almost been a wall of icicles here - like a curtain."
The Rutland and Masson caverns formed naturally millions of years ago and remain open to the public via guided walks.