ARX BRITANNICA, a citadel of Batavia, whose foundation is seen at low water, near the old mouth of the middle Rhine: some imagine it the Pharos, or high tower of Caligula, as Suetonius calls it; a monument of Caligula's ill-conceived conquest of Britain. Others, that it was built by Drusus, with an altar afterwards by Claudius, on his expedition into Britain. But the usual passage was from Gessoriacum; and Suetonius expressly says, Claudius passed over thence. The ancient name of this citadel, now covered by the sea, is no where expressed: now commonly called 't Huis Britten, or Brittenburg; that is, Arx Britannica; but from what authority does not appear.