At the end of the Akiyoshi-do cave there is an elevator which you can use up to the surface. Then there is a not to long uphill walk and you reach the Karst viewing platform. Also up there you find ice cream and a museum in a nearby building.
It's worth going to the viewing platform, especially if you arrived from Yamaguchi and intend to return that way because you'll want to see the Karst plateau.
On the plateau itself there are hiking paths. If you do plan some hiking then you better come prepared with water bottles and heavy sun protection as there is absolutely no shade at all.
The Akiyoshi-do can be visited every day and an entrance fee applies. I wanted to check the current price but the official website is in Japanese only.
The cave is huge and you can walk about 1,5 kilometers through it. There is also a small river running through it and you enter the cave where it exits. It is extremely difficult to photograph in the cave unless you have a tripod because light conditions don't allow you too much and you flash won't go that far.
The amazing thing about this cave is its sheer size. There are rock formations but there are certainly more exiting ones in other parts of the world.
Mind you, there is a cave near Kochi that I once visited. But that one was also very crowded and actually a disappointment because the formations had changed in colour due to all the visitors touching them.
One favourite thing in Akiyoshi-do was the lime stone terraces filled with water similar to the ones in Pammukale (Turkey), only here they are not white.
I had lunch in the restaurant by the viewing platform (Observatory) on the Karst plateau. This turned out quite an experience since I don't speak any Japanese. The noodles menu is handing there but in Japanese only and at the time when I was there, there were hardly any other people. The man there was quite desparate to help me and a lady came who didn't speak any English either except "beef". So I ended up with beef noodle soup but I'm sure there would have been nicer dishes.
Staff was trying their best to communicate somehow.
I took the bus from Hagi on the north coast and had a good introduction of the Karst tablelands. There are several bus stops with similar names, so make sure you get off the right one as walkings distances are great. If you take this bus and travel on a Japanese railpass then you will have to pay for it.
After my visit to the cave I took the JR bus to Yamaguchi, this one is covered by the Japanese railpass.
In the bus station building you will find toilets, luggage lockers, a tourist information and a café.
Once you arrive, you basically cross the street and following the pedestrian path through the souvenir shops and restaurants to the cave. On this stretch you will find all the souvenirs you need.