Rubens and his friend Jan Brueghel collaborated on a number of mythological and religious pictures about 1610-20. In this panel Rubens designed and painted the figure groups and Brueghel painted everything else. The river god Achelous explains to the Greek hero Theseus that a distant island is his former lover Perimele, transformed by Neptune so that she could remain forever within the river's embrace. The artists combined Latin learning, athletic nudes (some based on classical sculpture), the wonders of nature and some made by man into an encyclopedic display meant for a sophisticated collector.