Krakatau Volcanic Islands, Nestled between the large Indonesian islands of Java and Sumatra is the Krakatau Volcano National Park. In the fourth century, a single marine volcano stood at this site, but in 416 A.D., the caldera of the volcano collapsed. The remnants formed a new caldera, or volcanic feature formed by the collapse of land following an eruption, around 7 km in diameter, with the peak’s remnants becoming the three islands of Verlaten, Lang and Krakatau