Ancient Greek civilization originated in cities on the Greek mainland and islands in the Aegean Sea between 1100 BC and 146 BC. It started with the mingling of two Greek cultures, the Dorian and Ionian, and developed sedentary agricultural and commercial societies organized around independent city-states. Greek architecture began as temples to house the gods and evolved other civic buildings as Greek society developed. Religious belief centered on polytheism and elaborate temples were built to honor the gods, with architecture serving religious functions. Greek achievements extended to early science, arts, literature, and sports.