The Cathedral Caves are definitely the best feature of The Catlins. Situated on Waipati Beach there are two caves that connect at the back. At low tide the caves are accessible, and you can walk from one cave through to the next.
Cathedral caves is privately managed and costs $5 per person ($2 per child). We did not realise this, so have your $5 cash ready if you are headed to these caves. The caves are only open to the public just prior and just after low tide. They open about an hour before the schedule low tide, and stay open for about an hour and a half afterwards. You will need to check the tidal information. If you have time to kill (as we did), Papatowai Beach is not far away (about a 20 minute drive east), and you will be able to kill some time there before heading to the caves.
Once you are at the caves there is a large parking space and a 15-20 minute walk down a hill and onto the beach. Yes, you will have to walk back up this hill but the native forest and ferns provide for a nice distraction. The money you pay goes into track and carpark maintenance and similar ventures to keep this area open to the public. The caretakers you will meet along the way, you can pay them your money, get your ticket and head off. The beach itself is flat, and you can see for quite a way and has a fine, soft white sand. You have a 2-5 min walk across the beach before getting to the caves. This destination is very popular so I would try getting there as close to opening time as possible. The entrance is off a state highway with no room to pull off onto the side of the road however.
The Cathedral Caves will stun you. The cave stretches quite a way into the mountain and these caves are in the top 30 of longest caves in the world. Bet you didn’t think New Zealand had that to offer! You can walk through the most landward cave to access the more seaward cave. It is dark, you could take a head torch if you wished and I would suggest durable footwear (just to be on the safe side). I was too scared to tough the cave walls but my partner did and nothing jumped out at him. The water in the cave comes out a beautiful greeny-blue color and the walls are a soft pink hue which makes for gorgeous photos. I would rally suggest visiting this site. It is really one of the best places in New Zealand I have ever been.