In Chapter 3 of Johann David Wyss and Johann Rudolf Wyss's The Swiss Family Robinson, father and the eldest son Fritz go out to explore the island further. They venture upstream and find a place to safely cross the stream separating the beach from the rest of the island by climbing along the surfaces of rocks. They find beautiful birds, lots of coconuts, gourds to make dishes and utensils with, sugar cane, monkeys, and a rocky summit from which they could see that they are the only inhabitants on the island.
By Chapter 8, the family is hit by "week after week" of pouring rain that keeps then in doors. After the stormy season passes, father decides they need either a stronger shelter for the stormy season or some place safer to at least store their most perishable goods. Upon Fritz's suggestion, father decides to try "hollow out a cave" in nearby rock. However, as they are proceeding, Jack discovers a real cave when the crowbar he is using to make a whole in the rock slips "through the mountain." Father and the boys then chip away at the rest of the rock to reveal the cavern. After purifying the air in their newly found cave, the cave becomes safe to store goods in it during the winter.