Volcanic eruptions are still the subject of stories among the local people who speak fearfully of fire and evil spirits. The magnificent Shetani lava flow and caves are only 200 years old and are well worth investigating. You need to be extremely cautious if you plan to explore the caves and you must take a torch.
Chaimu lava flow has a walking trail which is fun, but the brittle black lava is not very stable and is bare of plants. It is possible to climb up to the crater rim, but it is very hard work. Also, keep in mind that the animals of Tsavo are not fenced in so, while caving, try not to disturb any of the potential sleeping beasts.