The early iron age lasted roughly a millennium until the rise of the first large-scale kingdoms (mandalas) in mainland Southeast Asia. This coincided with a remarkable culture located in the region of Xieng Khouang in Laos. This was the megalithic culture associated in its early (Hua Phan) phase with standing menhirs (preiron age) and in its later (Xieng Khouang) phase with the remarkable stone jars that give the Plain of Jars its name. These jars measure on average around 1.5 m in height and diameter, with some much larger, weighing as much as 15 tons. That these were part of a funerary cult is indicated by what appears to be a central crematorium at Ban Ang. Higham (1989) dates the jars to between the third century BCE and the third century CE.