CENTUMCELLÆ, in Ancient Geography, Trajan's villa in Tuscany, on the coast, three miles from Algæ; with an excellent port, called Trajanus Portus, (Ptolemy); and a factitious island at the mouth of the port, made with a huge block of stone, on which two turrets rose, with two entrances into the basin or harbour, (Rutilius). Now Civita Vecchia. E. Long. 12. 30. N. Lat. 42°.