Detail from a Roman cosmological mosaic, Augusta Emerita (Merida), Spain. The mosaic is in the so-called Mithraic House which dates from the 1st or early 2nd century AD. The mosaic gives a Roman view of the cosmos with the heavenly powers at the top the terrestrial powers in the middle and the world of water at the bottom.This image shows the Water deities, Oceanus, the god of the earth-encircling river and the regulator of the rising and setting of the heavenly bodies which were believed to emerge and descend into his watery realm; Euphrates, the river god of Assyria; Nilus, the god representing youth and Nile water and Portus. Also shown are Tranquillitas, the roman goddess of peace and security and copiae the roman goddess of plenty, here shown as representing a personification of seafaring.