SUNIUM, a promontory and demus of ancient Attica, forming the southern extremity of that country. The promontory, which rises steeply from the sea to a great height, was crowned with a temple to Athens, the tutelary deity of Athens. This temple is now in ruins, but many of its columns are still standing, and have given to the promontory its modern name of Cape Colonna. Sunium was fortified in the nineteenth year of the Peloponnesian war, in order to protect the corn-ships in their passage to Athens with supplies, and from that time onwards it was considered one of the chief fortresses of Attica.