Premise: Hundreds of ancient stone religious monuments lie on the island of Java. Known as "candi" in Indonesian, they date from the early classical period of Javanese civilisation, beginning in the first part of the 8th century CE and ending after 900 CE. The majority were built between 780 CE and 860 CE, even though the civilisation that created them existed for many centuries.
Hypothesis: The hundreds of stone monuments in Java were placed there by aliens