To make one thing clear: this page is about subterranean tourist sites on the island of Java, and has nothing to do with the computer language or the coffee of the same name. The island is part of Indonesia and the Capital Jakarta is located on the northern coast of the island. The island is 1,000km long and 210km wide, the total area is 139,000km², which makes it the 13th largest island in the world and the fifth largest in Indonesia. With 145 million inhabitants it is densely populated at 1,121 people/km².
Java was the first place where coffee was grown in Indonesia, during the early Dutch colonial period. The official starting date is 1699 with the successful growth of arabica coffee (Coffea arabica). After the Dutch governor of Malabar in India sent seedlings from Yemen to the Dutch governor of Batavia in 1696 the first batch failed due to a flood. But the second try in 1699 was successfull and in 1711 the first exports were sent to Europe. Today Indonesia is the fourth-largest producer of coffee in the world. Java is very fertile, a result of the climate and the volcanic origin.
The geology is mostly volcanic, as it was formed by the convergent plate rim between Sunda Plate and Australian Plate. Both are oceanic plates, so the subduction zone lies under water, but it causes volcanism, earthquakes, and the sediment on top of the oceanic crust is accumulated by the movement. As a result there are small patches of sedimentary rock found on the island.