The Republic of Indonesia is the world's largest island country, the Indonesian archipelago is a 5000 km long string of 13,677 islands stretching between Malaysia in the west and Australia in the east. The largest islands are Java, Sumatra, Borneo, Sulawesi, and New Guinea. Some belong only partly to Indonesia, like Borneo which is shared with Brunei and Malaysia, and New Guinea which is shared with Papua New Guinea. They are located around the equator between Asia and Australia, between the Indian and Pacific oceans. The country belongs to Southeast Asia, the population is Muslim, the capital is Jakarta.
The islands have numerous limestone areas and thus numerous karst caves. The three longest caves are currently [2023] Goa Luweng Jaran (18.2 km), Gua Salukkan Kallang (12.2. km), and Leang Assuloang (10.4 km). Sometimes they are mentioned on tourist pages, but neither is actually suitable for tourist visits. As far as we know, there are no cave trekking tours either.