Cultural development continues along patterns laid down in prior centuries. Jade and greenstone production increases considerably. Intricately carved metates, grinding tables for the processing of maize, were included in elite burials and may also have been used as thrones. Other forms of monumental sculpture occurred at the Panamanian site of Barriles, a sculptural tradition that influences southern Costa Rica. Metallurgy, focusing on the use of gold and copper, was introduced from northern Colombia perhaps as early as the third century. It moves steadily north thereafter.