A nice enough walk with an interesting couple of tunnels, but perhaps not quite worth the side trip given the other walks in the area. The original tunnel by the car park is currently closed due to rock fall inside the tunnel. A sign directs you 50 m up the road - passed one other blocked tunnel - to the alternative trail head. This will be obvious when you get to it and starts with a boardwalk through a tunnel. Like most walks in the area, the winding path takes you through forest, occasionally on board walks, but with the added bonus of an extra tunnel which you can climb down into and walk along. It's 40-50 m long and opens into forest but with no where further to go, so head back through the same tunnel. A torch will help for this one as the floor is not even and very slippery clay.
Highly recommended short walk, we went while it was drizzling so quite magical. Take a torch for the first and last part of the trek. The middle cave looked to dangerous due to weather so we didnt risk going in for a closer look.