Caves in Nigeria are common places for tourists to visit. Ogbunike caves are no exception. They are located in the city of the same name and are limestone. Some believe it. that they can treat various diseases. Here
https://keckcaves.org/ogbunike-caves-nigeria/ has more information about it and videos. You can also find a lot of interesting things in the The Ogbunike Caves in Nigeria search engine.