Culdee Caves is a famous landmark on the Skarloey Railway, located above Great Waterton and beneath Culdee Fell Hill. Originally Duncan was going to take holidaymakers to see the Culdee Caves, however his job was given to Bertie instead. Duncan actually did explore the caves when he passed the barriers blocking the tracks, covered by some bushes. However, his funnel damaged a roof support, trapping himself. He eventually found a way out when he found some coal trucks and another entrance.
It was only seen in Duncan and the Old Mine.