A 30-metre “pyramid” submerged just off the coast of Japan is turning heads — and could shake up everything we thought we knew about ancient civilisations.

The enormous stone structure, complete with angular steps and flat terraces, looks uncannily like the ruins of a man-made temple — despite being over 10,000 years old.

Gunung Padang, first re-discovered by Dutch explorers in 1890, is said to be the world's oldest pyramid. Studies show that ...