If you only do one thing in Gopeng, explore the 'Coconut Cave', named for its domelike interior. The easy option is the 'Golden Flowstone' walk, a self-guided 40-minute stroll along boardwalks that wind between hulking stalactites. Or you can get thrillingly wet and muddy on scrambles of various lengths through the cave tunnels (book ahead – not for the claustrophobic). It's 9km south and east from Gopeng town; follow Rte 1 and the signs.
If you don't have your own transport, many resorts in Gopeng arrange tours. Last entry 4.15pm.