The first temples were mostly mud, brick, and marble structures on stone foundations. The columns and superstructure (entablature) were wooden, door openings and antae were protected with wooden planks. The mud brick walls were often reinforced by wooden posts, in a type of half-timbered technique.
It would be "Indonesia" that is not a country of mainland Southeast Asia," since Indonesia is in fact a large groups of islands off the coast, located above Australia.
